Cell culture

ABSTRACT

There is described an isolated 3-dimensional liver spheroid wherein said spheroid has: increased ATP content as compared to a 3-dimensional liver spheroid cultured in Complete William&#39;s E medium alone; the same or increased activity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a 3-dimensional liver spheroid cultured in Complete William&#39;s E medium alone; and increased albumin secretion as compared to a 3-dimensional liver spheroid cultured in William&#39;s E medium alone.

This application is a U.S. National Stage Application of InternationalApplication No. PCT/EP2017/070881 filed Aug. 17, 2017, which waspublished in English on Mar. 1, 2018, as International Publication No.WO 2018/036910 A1. International Application No. PCT/EP2017/070881claims priority to European Application No. 16185725.5 filed Aug. 25,2016.

FIELD OF THE INVENTION

The present invention relates to the field of cell culture, inparticular, to the culture of 3-dimensional cells, 3-dimensionalco-cultures and methods and uses thereof.

BACKGROUND

Toxicological studies using 2-dimensional cell culture systems have beenused to examine the effects of drugs on cell survival and enzymeactivity etc. While being able to grow cells in flat layers on plasticsurfaces is straight forward and permits the study of several aspects ofthe cellular physiology and responses to stimuli, they do not reflectthe real structure and architecture of an organ. In 2-dimensionalmonolayers, the extracellular matrix, the cell-to-cell andcell-to-matrix interactions, which are essential for thedifferentiation, proliferation and cellular functions are lost.

3-dimensional culture systems can form a functional tissue with similarfeatures to those observed in vivo. As compared to the 2-dimensionalculture systems, 3-dimensional cell culture allows cells to interactwith their surroundings in all three dimensions and are morephysiologically relevant. Such cells can show improvements in viability,proliferation, differentiation, morphology, response to stimuli, drugmetabolism, gene expression and protein synthesis and the like.3-dimensional cell culture can produce specific tissue-like structuresand mimic functions and responses of real tissues in a manner that ismore physiologically relevant than traditional 2-dimensional cellmonolayers.

Several 3-dimensional tissues mimicking human organs are commerciallyavailable. Lung 3-dimensional organotypic tissues for example can beprepared using primary human cells grown at the air-liquid interface(ALI) where these cells will differentiate and form a functional tissue.These 3-dimensional tissues bear close morphological resemblance andmetabolic characteristics to human bronchial tissues. They are composedof basal, goblet and ciliated cells arranged in a pseudostratifiedstructure. Similar to the lung, actively beating cilia are presentallowing the study of their function and activity. Similar levels ofxenobiotic enzyme-encoding mRNA have been found in these 3-dimensionalALI cultures compared with human lungs. In addition, these tissues canbe maintained in vitro for an extended period of time. This3-dimensional model of lung tissue is an appropriate model to explorethe effects of aerosols and drugs etc., and also to observe the effectof repeated exposure.

Other 3-dimensional models have also been described, including3-dimensional liver spheroid models. Liver spheroids can be composed ofseveral cell types that were initially used in 2-dimensional cultures todetermine the effects of drug treatments on liver cells. However,primary human hepatocytes do not express metabolic enzymes for more than5 days, despite having similar phase 1 metabolic gene expressioncompared with human liver tissues. Another limitation is the shortviability that makes repeated dosing difficult. These drawbacks can beovercome by the use of alternative, long-lived liver cell lines such asHepaRG cells (ThermoFisher Scientific). HepaRG cells are a human hepaticprogenitor cell line that retain many characteristics of primary humanhepatocytes. They have a greater liver-specific and phase 1 metabolicgene expression compared to primary hepatocytes. In addition, theirlifespan is strongly increased. Formation of HepaRG cells in3-dimensional spheroids increases lifespan and metabolic capabilities.

The interest in liver-dependent toxicological studies pertains to theability of this tissue to metabolize several compounds by xenobioticmetabolism. While many chemical compounds are inactivated andsolubilized, some are bio-activated and therefore become toxic. As aconsequence, studying the toxicity of a compound in an organ withouttaking into account the bio-activation process taking place in the livermight lead to underestimated toxic effects of the tested substances.Hence, in the field of aerosol exposure, there is a need for an improvedapproach to study the penetration of a substance in the lung and itsfurther bio-activation in the liver. The present invention seeks toaddress this need in the art.

SUMMARY

In the present disclosure, individual lung and liver cultures have beenestablished and characterised morphologically and functionally. In orderto facilitate the co-culture of both cell types, cell culture conditionsand specifically cell culture media have been identified so that bothlung and liver cultures maintain viability, structural integrity andfunctional capabilities. Advantageously, this makes it possible todevelop a multiple organ system that recreates the interaction betweenthe lung and the liver and, significantly, without the loss of each ofthe cells individual characteristics. The finding herein that lungepithelial cell culture medium can be used to successfully grow andmaintain liver spheroids and can even significantly improve thecharacteristics of the liver spheroids was wholly unexpected. Using thismultiple organ system will greatly assist in understanding the role ofthe liver on the metabolism of lung-absorbed compounds—such as aerosols.The present disclosure provide a valuable tool to study the impact ofcompounds in a 3-dimensional, cell culture system that is closer, andthus is expected to be more predictive, of the clinical situation andoffer a unique, simple and inexpensive 3-dimensional liver and lung cellco-culture system.

ASPECTS AND EMBODIMENTS OF THE PRESENT INVENTION

In a first aspect, there is provided an isolated 3-dimensional liverspheroid, wherein the spheroid has: increased ATP content as compared toa 3-dimensional liver spheroid cultured in Complete William's E mediumalone; the same or increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone; and increased albuminsecretion as compared to a 3-dimensional liver spheroid cultured inWilliam's E medium alone.

The term “Complete William's E medium alone” means a culture mediumconsisting of Complete William's E medium only, that is a culture mediumconsisting of 100% (v/v) Complete William's E medium.

In another aspect, there is provided an isolated 3-dimensional liverspheroid for use in a 3-dimensional multi-organ culture system obtainedor obtainable by a process comprising: culturing a 3-dimensional liverspheroid in a cell culture medium comprising or consisting or consistingessentially of either: (a) Complete PneumaCult-ALI medium; or (b)Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium, for a period of time that is sufficient to obtain a3-dimensional liver spheroid in which: ATP content is increased ascompared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone; cytochrome P450 1A1 and cytochrome P450 1B1activity is the same or increased as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone; and albuminsecretion is increased as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone.

Suitably, the spheroid is or is derived from a human hepatic progenitorcell line, suitably, wherein the spheroid is or is derived from a HepaRGcell.

Suitably, the spheroid is cultured in a cell culture medium comprisingor consisting or consisting essentially of either: (a) CompletePneumaCult-ALI medium; or (b) Complete B-ALI medium; (c) CompletePneumaCult-ALI medium and Complete William's E medium, or (d) CompleteB-ALI medium and Complete William's E medium.

In a further aspect, there is provided a co-culture comprising the3-dimensional liver spheroid according to any of the preceding claimsand a 3-dimensional lung epithelial cell.

Suitably, the co-culture is maintained in a cell culture mediumcomprising or consisting or consisting essentially of either: (a)Complete PneumaCult-ALI medium; or (b) Complete B-ALI medium; or (c)Complete PneumaCult-ALI medium and Complete William's E medium, or (d)Complete B-ALI medium and Complete William's E medium. In a furtheraspect, there is provided 3-dimensional organ culture system comprisingthe isolated 3-dimensional liver spheroid described herein.

In a further aspect, there is provided a 3-dimensional multi-organculture system comprising the isolated 3-dimensional liver spheroid asdescribed herein and further comprising at least one other 3-dimensionalcell type, or comprising the co-culture described herein.

Suitably, the 3-dimensional liver spheroid is submerged in culturemedium contained on the culture system.

Suitably, the 3-dimensional multi-organ culture system further comprisesa 3-dimensional lung epithelial cell, suitably, wherein the3-dimensional lung epithelial cell is at an air liquid interface on the3-dimensional multi-organ culture system.

In a further aspect, there is provided a 3-dimensional multi-organculture system comprising: (a) a first organ growth section comprising afirst organ cavity adapted to submerge a first 3-dimensional cell typein a culture medium; (b) a second organ growth section comprising asecond organ cavity adapted to culture a second 3-dimensional cell typeat an air liquid interface, the second 3-dimensional cell type being acell type that is different than the first 3-dimensional cell type; and(c) a culture medium reservoir connecting the first organ cavity and thesecond organ cavity to allow for the flow of culture medium therebetween.

Suitably, the first organ cavity and second organ cavity contain thesame culture medium.

Suitably, the 3-dimensional multi-organ culture system comprises theco-culture described herein.

Suitably, the 3-dimensional organ culture system or the 3-dimensionalmulti-organ culture system is miniaturised.

Suitably, the 3-dimensional organ culture system or the 3-dimensionalmulti-organ culture system comprises or is a microfluidic device,suitably, wherein said system is an organ-on-a-chip.

In a further aspect, there is provided a cell culture medium comprisingor consisting or consisting essentially of: (a) a mixture of CompletePneumaCult-ALI medium and Complete William's E medium; or (b) a mixtureof Complete B-ALI medium and Complete William's E medium.

Suitably, the cell culture medium further comprises the 3-dimensionalliver spheroid or the co-culture described herein.

In a further aspect, there is provided a 3-dimensional multi-organculture system comprising a culture medium, said culture medium selectedfrom the group consisting of a culture medium comprising or consistingor consisting essentially of either: (a) Complete PneumaCult-ALI medium;or (b) Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium or a combination of two or more thereof.

In a further aspect, there is provided a method of preparing a3-dimensional liver spheroid for use in a 3-dimensional organ culturesystem comprising: (i) providing a 3-dimensional liver spheroid; (ii)contacting the 3-dimensional liver spheroid with a culture mediumcomprising or consisting or consisting essentially of either: (a)Complete PneumaCult-ALI medium; or (b) Complete B-ALI medium; or (c)Complete PneumaCult-ALI medium and Complete William's E medium, or (d)Complete B-ALI medium and Complete William's E medium; and (iii)obtaining a 3-dimensional liver spheroid for use in a 3-dimensionalorgan culture system.

In a further aspect, there is provided a method of preparing aco-culture comprising or consisting or consisting essentially of a3-dimensional liver spheroid and a 3-dimensional lung epithelial cellfor use in a 3-dimensional multi-organ culture system comprising: (i)providing a 3-dimensional liver spheroid and a 3-dimensional lungepithelial cell; (ii) contacting the 3-dimensional liver spheroid andthe 3-dimensional lung epithelial cell with a culture medium comprisingor consisting or consisting essentially of either: (a) CompletePneumaCult-ALI medium; or (b) Complete B-ALI medium; or (c) CompletePneumaCult-ALI medium and Complete William's E medium, or (d) CompleteB-ALI medium and Complete William's E medium; and (iii) obtaining aco-culture of a 3-dimensional liver spheroid and a 3-dimensional lungepithelial cell.

In a further aspect, there is provided an in vitro method for assessingthe response of a 3-dimensional liver spheroid to an agent, the methodcomprising: (i) contacting the 3-dimensional liver spheroid or theco-culture or the 3-dimensional organ culture system, or the3-dimensional multi-organ culture system as described herein with atleast one agent; and (ii) measuring one or more responses of the3-dimensional liver spheroid or the co-culture or the 3-dimensionalorgan culture system or the 3-dimensional multi-organ culture systemafter contact with the at least one agent; wherein a difference in theone or more responses before and after contact with the at least oneagent is indicative that the agent modulates the response of the cell.

In a further aspect, there is provided an in vitro method for assessingthe response of a 3-dimensional liver spheroid and a 3-dimensional lungepithelial cell to an agent, the method comprising: (i) contacting theco-culture or the 3-dimensional organ culture system or the3-dimensional multi-organ culture system with at least one agent; and(ii) measuring one or more responses of the co-culture or the3-dimensional organ culture system or the 3-dimensional multi-organculture system after contact with the at least one agent; wherein adifference in the one or more responses before and after contact withthe at least one agent is indicative that the agent modulates theresponse of the cell.

Suitably, step (ii) comprises measuring the penetration of the at leastone agent into the 3-dimensional lung epithelial cell.

Suitably, the in vitro method comprises the further step of: (iii)measuring the bio-activation of the at least one agent in the3-dimensional liver spheroid; wherein the measurements in steps (ii) and(iii) are carried out simultaneously or wherein the measurement in step(iii) is carried out after the measurement in step (ii).

Suitably, the agent is an aerosol, more suitably, the aerosol is or isderived from smoke, suitably, cigarette smoke.

In a further aspect, there is provided the use of a cell culture mediumcomprising or consisting or consisting essentially of either: (a)Complete PneumaCult-ALI medium; or (b) Complete B-ALI medium; or (c)Complete PneumaCult-ALI medium and Complete William's E medium, or (d)Complete B-ALI medium and Complete William's E medium, for culturing a3-dimensional liver spheroid or a 3-dimensional lung epithelial cell orfor co-culturing a 3-dimensional liver spheroid and a 3-dimensional lungepithelial cell.

In a further aspect, there is provided the use of the 3-dimensionalorgan culture system or the 3-dimensional multi-organ culture system asdescribed herein for toxicity testing or for drug discovery or fordetermining the penetration of an agent into lung cells and/or fordetermining the bio-activation of an agent in liver cells, suitably,wherein the agent is an aerosol.

A further aspect relates to a liver spheroid, a co-culture, a3-dimensional organ culture system, a 3-dimensional multi-organ culturesystem, a cell culture medium, a method or a use substantially asdescribed herein and with reference to the accompanying description anddrawings.

Further particular and preferred aspects are set out in the accompanyingindependent and dependent claims. Features of the dependent claims maybe combined with features of the independent claims as appropriate, andin combinations other than those explicitly set out in the claims.Combinations of one or more of the embodiments set forth above aretherefore also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Schematic overview of experimental design and endpoints for thecharacterisation of 3-dimensional organotypic lung tissues (GEx: Geneexpression).

FIG. 2. Schematic overview of experimental design and endpoints for thecharacterization of liver spheroids (GEx: Gene expression).

FIG. 3. Hematoxylin & eosin and Alcian blue staining of 3-dimensionalorganotypic lung cultures at 1, 2, 3, and 4 weeks following maturation.Representative cross-sections of epithelium are shown at 20×magnification.

FIG. 4. ATP content of 3-dimensional organotypic lung cultures ismeasured at 1, 2, 3, and 4 weeks following maturation. Results for 3independent measurements are shown. Rep: Replicate; RLU: Relative lightunit

FIG. 5. ATP secretion into the apical surface liquid of 3-dimensionalorganotypic lung cultures is measured in response to stimulation withhypotonic saline at 1, 2, 3, and 4 weeks following maturation. Resultsfor 6 independent measurements are shown. Rep: Replicate

FIG. 6. Cytochrome P450 1A1/B1 activity is measured in 3-dimensionalorganotypic lung cultures at 1, 2, 3, and 4 weeks following maturation.Results show basal CYP activity, induced activity following 48-htreatment with TCDD and rifampicin, and induced activity followinginhibition with α-naphtoflavone. Results are presented as mean±SEM of 3independent experiments. The dotted line indicates the trend based onthe average value per time point.

FIG. 7. Fold regulation of the expression of phase 1 drug metabolismenzyme-encoding genes in 3-dimensional organotypic lung cultures isassessed at 1, 2, 3, and 4 weeks. Gene expression is compared betweenlung cultures treated with TCDD and rifampicin for 48 hours (n=3) anduntreated cultures (n=3), and fold changes are calculated using the ΔΔCTmethod. The heatmaps list the 20 most up—(in red, on the left) anddown-regulated genes (in blue, on the right) together with the foldchange. Gene symbols are displayed on the left side of the heatmaps.

FIG. 8. Liver spheroids stained for cytokeratin 19 expression at 1, 2,3, and 4 weeks following maturation. Shown are representative images inpseudocolors (CK19 in red, nuclei in blue) at 10× magnification.

FIG. 9. Total ATP content of liver spheroids and their conditioned mediais measured at 1, 2, 3, and 4 weeks following maturation. Results for 3independent measurements are shown. Rep. Replicate

FIG. 10. Albumin secretion from liver spheroids is quantified at 1, 2,3, and 4 weeks following maturation Results for 8 independentmeasurements are shown. The dotted line indicates the trend based on theaverage value per time point. Rep: Replicate; Alpha-GST production byliver spheroids is assessed at 1, 2, 3, and 4 weeks followingmaturation. Results for 8 independent measurements are shown. Rep:Replicate; Cytochrome P450 1A1/B1 activity is measured in liverspheroids at 1, 2, 3, and 4 weeks following maturation. Results showbasal CYP activity, induced activity following 48-h treatment with TCDDand rifampicin, and induced activity following inhibition withα-naphtoflavone. Results are presented as mean±SEM of 3 independentexperiments; Cytochrome P450 1A2 activity is measured in liver spheroidsat 1, 2, 3, and 4 weeks following maturation. Results show basal CYPactivity, induced activity following 48-h induction with TCDD andrifampicin, and induced activity following inhibition with fluvoxaminemaleate. Results are presented as mean±SEM of 3 independent experiments.

FIG. 11. Total ATP content of liver spheroids and their conditionedmedia is measured following culture in mixtures of William's E andComplete B-ALI medium or Complete PneumaCult-ALI medium (StemCellTechnologies, Grenoble, France). Results are presented as mean±SEM for 5independent measurements; Cytotoxicity is measured in liver spheroidsfollowing culture in mixtures of William's E and Complete B-ALI mediumor Complete PneumaCult-ALI medium. Results are presented as mean±SEM for5 independent measurements. RFU: Relative fluorescence units

FIG. 12. Apoptosis is measured in liver spheroids following culture inmixtures of William's E and Complete B-ALI medium or CompletePneumaCult-ALI medium medium. Results are presented as mean±SEM for 5independent measurements; CYP1A1/B1 activity is measured in liverspheroids following culture in mixtures of William's E and CompleteB-ALI medium or Complete PneumaCult-ALI medium. Results are presented asmean±SEM for 3 independent measurements.

DETAILED DESCRIPTION

The practice of the present disclosure employs, unless otherwiseindicated, conventional techniques of molecular biology, microbiology,cell biology and biochemistry. Such techniques are explained fully inthe literature, such as, in Molecular Cloning: A Laboratory Manual,second edition (Sambrook et al., 1989) Cold Spring Harbor Press;Oligonucleotide Synthesis (M J. Gait, ed., 1984); Methods in MolecularBiology, Humana Press; Cell Biology: A Laboratory Notebook (J. E. CelMs,ed., 1998) Academic Press; Animal Cell Culture (R. I. Freshney, ed.,1987); Introduction to Cell and Tissue Culture (J. P. Mather and P. E.Roberts, 1998) Plenum Press; Cell and Tissue Culture: LaboratoryProcedures (A. Doyle, I B. Griffiths, and D. G. Newell, eds., 1993-8) J.Wiley and Sons; Methods in Enzymology (Academic Press, Inc.); CurrentProtocols in Molecular Biology (F. M. Ausubel et al., eds., 1987); PCR:The Polymerase Chain Reaction, (Mullis et al., eds., 1994). Proceduresemploying commercially available kits and reagents will typically beused according to manufacturer-defined protocols unless otherwiseindicated.

The technical terms and expressions used herein are generally to begiven the meaning commonly applied to them in the pertinent art ofmolecular biology, microbiology, cell biology and biochemistry. All ofthe following term definitions apply to the complete content of thisapplication.

The term “comprising” does not exclude other elements or steps.

The term “consisting essentially of” refers to those elements requiredfor a given embodiment. The term permits the presence of elements thatdo not materially affect the basic and novel or functionalcharacteristic(s) of that embodiment. The term allows the presence ofother components or ingredients in addition to the components oringredients recited, provided that the essential characteristics of thecomposition are not materially affected by their presence. In thecontext of a cell culture medium, the term permits the presence ofelements or ingredients that do not materially affect the basic andnovel or functional characteristic(s) of the cell culture medium. Theterm allows the presence of other elements or ingredients in addition tothe elements or ingredients recited, provided that the essentialcharacteristics of the cell culture medium are not materially affectedby their presence. For example, the term allows the presence of otherelements or ingredients in addition to the elements or ingredientsrecited, provided that the essential characteristics of cells culturedin the cell culture medium are not materially affected by their presenceas compared to cells cultured in a cell culture medium that does notinclude the other elements or ingredients.

The indefinite article “a” or “an” does not exclude a plurality.

Cell Culture

Cell culture generally refers to the removal of cells from a tissueprior to growth in an artificial environment. The cells to be culturedcan be removed directly from a tissue containing the cell to be culturedand optionally treated with enzymatic or mechanical means prior toculture. As an alternative, the cells to be cultured can be derived froma prior established strain or line of cell. Cell culture can provide asystem for studying various aspects of a cell including the physiology;the biochemistry; the effects of drugs or compounds, including aerosols;the screening and development or optimisation of drugs or compounds; thestudy of drug or compound efficacy; the study of drug or compoundabsorption; toxicity screenings; toxicology; target discovery;pharmacokinetics; pharmacodynamics; and regenerative medicine.

Cells grow in an artificial environment containing a cell culture mediumthat supplies growth factors, hormones, gases and essentialnutrients—such as vitamins, amino acids, carbohydrates, minerals and thelike, and in which the artificial environment is regulated, for example,in terms of temperature, pH and pressure. Some cells require anchorageto a solid or semi-solid substrate while other cells can grow whilstfloating in a culture medium.

The present disclosure includes the use of “3-dimensional cell culture”,which includes any method that provides for the culture of a cell in 3dimensions, with or without the use of a matrix or scaffold. A number ofdifferent 3-dimensional cell culture methods have been developedincluding, spheroid cultures and organotypic cultures. Spheroid systems,especially liver spheroid systems, are of particular interest in thepresent disclosure.

Spheroids

The term “spheroid” assumes the meaning as normally understood in theart which is either a single cell that divides into a ball of cells in3-dimensions, or an aggregation of multiple cells in 3-dimensions,either with or without the use of a matrix or scaffold to support in3-dimensional cell growth within the spheroid. The 3-dimensionalspheroid can be an adherent spheroid or a spheroid grown in suspension.

Several different systems for culturing spheroids are available,including spheroids grown as aggregates, for example, on nanocultureplates, in suspension culture, on gels, on plastic coated withpoly-HEMA, via cell encapsulation or as aggregates via a hanging dropletsystem. Other methods include the use of spinner flasks, rotationsystems, concave plate methods and liquid-overlay. Bioreactors can alsobe adapted for use in 3-dimensional spheroid cell culture. In oneembodiment, the method used is the hanging droplet system—such as theGravityPLUS Hanging Drop System (InSphero). This method involves the useof the GravityTRAP ULA Plate which is a non-adhesive coated microtiterplate designed for the production of spheroids. Spheroid maturationtypically occurs within 2 to 5 days of seeding depending on the celltype and culture conditions. Suitably, the spheroids are cultured in avolume of 100 μl or more, or 200 μl more, or 300 μl or more. Suitably,the spheroids are cultured in Corning® spheroid microplates.

3-dimensional cell culture matrices or scaffolds can be used forspheroid culture. These are often porous substrates that can support3-dimensional cell growth and differentiation. A variety of materialshave been developed to produce 3-dimensional scaffolds with differencesin physical appearance, porosity, permeability, mechanicalcharacteristics, and nano-scale surface morphology. Examples of suchmaterials include: collagen gels, sponges or biogels; fibrin;fibronectin; laminin; alginates, hydrogels; cross-linkedglycosaminoglyca; polymer-based scaffold, synthetic scaffolds; peptidescaffolds; and chitosan composite scaffolds.

3-dimensional spheroids more closely resemble in vivo tissue in terms oftheir cellular communication and development of extracellular matrices.These matrices assist the cells in moving within the spheroid similar tothe way cells would move in living tissue. The spheroids are thus muchimproved models for differentiation, survival, cell migration, cellpolarisation, gene expression and growth.

Spheroids can be harvested and studied using various methods well knownin the art, including colorimetric, fluorescence, and luminescenceassays measured with a plate reader or they can be readily observed bymicroscopy. Additional techniques include western, northern or southernblot, histological techniques (for example, immunohistrochemistry, insitu hybridization, immunoflourescence) and the like. The use of opticalimaging methods—such as inverse bright field microscopy, fluorescencemicroscopy, single-photon emission computed tomography (SPECT), positronemission topography (PET), magnetic resonance imaging (MRI) and Cerenkovluminescence imaging (CLI) techniques is also contemplated.

Applications of the use of 3-dimensional spheroids include the study ofthe proliferation of cells and tissues in vitro in an environment thatmore closely approximates that found in vivo, the screening ofcompounds, toxicology assays, cell therapy, cell delivery, drugdelivery, biochemical replacement, production of biologically activemolecules, tissue engineering, biomaterial, and clinical trials.

The use of spheroids in 3-dimensional cell culture is generally reviewedin Expert Opin. Drug Discov. (2015) 10, 519-540.

In one embodiment, the spheroid is or is derived from a liver cell toform a 3-dimensional liver spheroid. Such liver spheroids can beprepared using various methods that are known in the art and describedin, for example, ALTEX (2014) 31, 441-477 and Toxicol. Sci. Off. J. Soc.Toxicol. (2013) 133, 67-78.

One aspect relates to an isolated 3-dimensional liver spheroid whereinsaid spheroid has: increased ATP content as compared to a 3-dimensionalliver spheroid cultured in Complete William's E medium alone; the sameor increased activity of cytochrome P450 1A1 and cytochrome P450 1B1 ascompared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone; and increased albumin secretion as compared toa 3-dimensional liver spheroid cultured in Complete William's E mediumalone.

Another aspect relates to an isolated 3-dimensional liver spheroid foruse in a 3-dimensional multi-organ culture system obtained or obtainableby a process comprising: culturing a 3-dimensional liver spheroid in acell culture medium comprising or consisting or consisting essentiallyof either: (a) Complete PneumaCult-ALI medium; or (b) Complete B-ALImedium; or (c) Complete PneumaCult-ALI medium and Complete William's Emedium, or (d) Complete B-ALI medium and Complete William's E medium,for a period of time that is sufficient to obtain a 3-dimensional liverspheroid in which: ATP content is increased as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; cytochrome P450 1A1 and cytochrome P450 1B1 activity is the sameor increased as compared to a 3-dimensional liver spheroid cultured inComplete William's E medium alone; and albumin secretion is increased ascompared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid can show improvedcharacteristics as compared to isolated 3-dimensional liver spheroidsgrown in cell culture medium previously optimised for the culture ofliver cells—such as William's E medium.

The isolated 3-dimensional liver spheroids can have increased ATPcontent, the same or increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 and increased albumin secretion as compared to anisolated 3-dimensional liver spheroid cultured in Complete William's Emedium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 1.5 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 1.0 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured inComplete William's E medium alone and increased albumin secretion thatis at least 1.9 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.1 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 1.9 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured inComplete William's E medium alone and increased albumin secretion thatis at least 1.8 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.1 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 2.1 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured inComplete William's E medium alone and increased albumin secretion thatis at least 2.0 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.4 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 2.4 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured inComplete William's E medium alone and increased albumin secretion thatis at least 2.1 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.9 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 2.3 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured inComplete William's E medium alone and increased albumin secretion thatis at least 2.6 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.6 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 2.9 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured incomplete William's E medium alone and increased albumin secretion thatis at least 2.5 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.7 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 2.1 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured incomplete William's E medium alone and increased albumin secretion thatis at least 3.3 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

The isolated 3-dimensional liver spheroid can have an ATP content thatis at least 2.7 fold higher than an isolated 3-dimensional liverspheroid cultured in Complete William's E medium alone, cytochrome P4501A1 and cytochrome P450 1B1 activity that is at least 2.6 fold higher ascompared to an isolated 3-dimensional liver spheroid cultured incomplete William's E medium alone and increased albumin secretion thatis at least 3.1 fold higher as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

Methods of measuring ATP content, cytochrome P450 1A1 and cytochromeP450 1B1 activity and albumin secretion are described herein.

Suitably, the isolated 3-dimensional liver spheroid when grown inculture has the same number or an increased number of necrotic cells ascompared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid when grown inculture has an increased number of apoptotic cells as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone.

Suitably, the isolated 3-dimensional liver spheroid has modulated (forexample, increased or decreased) levels of glutathione (GSH) as comparedto a 3-dimensional liver spheroid cultured in Complete William's Emedium alone.

Suitably, the isolated 3-dimensional liver spheroid has increased levelsof oxidized glutathione (GSSG) as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone.

Suitably, the changes described herein are observed after 9 days ofculture.

The use of co-cultures is also contemplated. In one aspect, there isprovided a co-culture comprising the 3-dimensional liver spheroid asdescribed herein together with at least one other cell type, suitably, a3-dimensional lung epithelial cell. Suitably, the co-culture ismaintained in a cell culture medium as described herein.

In one embodiment, the spheroid is or is derived from a lung cell toform a 3-dimensional lung spheroid. Such lung spheroids can be preparedusing various methods that are known in the art, such as those describedin ALTEX (2014) 31, 441-477 and Toxicol. Sci. Off. J. Soc. Toxicol.(2013) 133, 67-78.

Cell Sources

The present disclosure utilises various cell types including lung cellsand liver cells. Cells and cell lines for use in the present disclosurecan be isolated from a tissue or a fluid using methods that are wellknown in the art. Cells and cell lines for use in the present disclosurecan be differentiated from stem cells—such as embryonic stem cells orinduced pluripotent stem cells, or directly differentiated from somaticcells. Cells and cell lines may be or may be derived from human oranimal subjects or from human or animal cells, including any of a numberof mammalian species, suitably human, but including rat, mouse, pig,rabbit, and non-human primates and the like. Cells and cell lines can beobtained from commercial sources.

Lung cells—including lung epithelial cells—are one cell type ofinterest. Bronchial and/or airway epithelial cells are of particular usein the present disclosure. Human bronchial epithelial cells can becollected by brushing donor lungs during a bronchoscopy procedure. Inone embodiment, the lung cells are Normal Human Bronchial Epithelial(NHBE) cells. The lung epithelial cells can be cultured as a monolayerof undifferentiated cells or further developed into an organotypic lungepithelium-like tissue at an air-liquid interface. Cells can beestablished at an air-liquid interface using the following methodology.Briefly, epithelial cells can be cultured in a flask to increase thenumber of cells. After a period of incubation, cells are detached fromthe flask, counted and seeded onto inserts. On these inserts, cells areincubated with medium on the apical and basal sides. This phase ensurethat the cells will divide and completely cover the insert to form anepithelium. Then, apical medium is removed, the basal medium is retainedand replaced with a more complete medium. Cultures are incubated likethis for a further period of time. In the meantime, the cells willdifferentiate into 3 cell types: basal, goblet and ciliated cells. Atthe end of the maturation, the cultures are ready to use. The use of theair liquid interface to culture human nasal epithelial cells isdescribed in J Vis Exp. 2013; (80): 50646.

Lung epithelial cells can be obtained from human or animal subjects withdifferent pathologies, including subjects that are classified as smokersor non-smokers.

Liver cells are another cell type of interest. In one embodiment, thecells used are hepatocytes. Hepatocytes are cells of the liver, whichmake up 70-85% of the liver's cytoplasmic mass. The functionality ofhepatocytes is highly dependent on their capacity to form a polarphenotype, which is only established in 3-dimensional culture. Onesource of liver cells is primary hepatocytes which are an in vitro modelwidely used to investigate numerous aspects of liver physiology andpathology. The technique used to isolate human hepatocytes can be basedon a two-step collagenase perfusion of a donated liver. However, thesecells do not express metabolic enzymes for more than 5 days. Anotherlimitation is their short viability. These drawbacks can be overcome bythe use of alternative, long-lived liver cell lines—such as human oranimal hepatic progenitor cell lines. One such example of a humanhepatic progenitor cell line is the HepaRG cell line (ThermoFisherScientific). HepaRG cells retain many characteristics of primary humanhepatocytes. They have greater liver-specific and metabolic geneexpression compared to primary hepatocytes and a longer lifespan.Reorganisation of HepaRG cells in 3-dimensional spheroids furtherincreases both the lifespan and metabolic capabilities, suggesting thatspheroids may provide a better alternative in vitro liver model fortoxicity testing. Liver spheroids can also be created with a mixture ofprimary hepatocytes and liver stellate cells or primary hepatocytes andadipose tissue-derived stem cells.

In one embodiment, the lung cell is a lung epithelial cell—such as abronchial and/or airway epithelial cell.

In one embodiment, the liver cell is a HepaRG cell, suitably, a spheroidHepaRG cell. Combinations of cells are also contemplated, includingcombinations of liver and lung cells. The combination of a lungepithelial cell—such as a bronchial and/or airway epithelial cell, and aHepaRG cell, suitably, a spheroid HepaRG cell is contemplated. Oneaspect of the present disclosure relates to a 3-dimensional multi-organculture system. This culture system can comprise the use of variouscells—such as liver cells and a lung cells as described herein. The useof other cell types is also contemplated including, but not limited to,endothelial cells, (lung) fibroblasts and immune cells—such asmonocytes/macrophages, dendritic cells, neutrophils and mast cells.

In one embodiment, the methods of the present disclosure exclude thestep of isolating or obtaining a cell sample from a subject.

Cell Culture Media

One aspect of the present disclosure relates to cell culture media thatcan be used to culture 3-dimensional cells. In one embodiment, the cellculture media can be used to culture liver and lung cells without theloss of each of the cells individual characteristics. The liver cellsthat are cultured in the media described herein can even show improvedcharacteristics as compared to liver cells grown in cell culture mediumpreviously optimised for the culture of liver cells—such as Williams Emedium. Suitably, the lung cells retain their characteristics asdescribed herein. The media described herein can be used for the cultureof liver cells or the culture of lung cells or the co-culture of livercells and lung cells.

Suitably, liver cells grown in the cell culture medium/media can haveincreased ATP content, the same or increased activity of cytochrome P4501A1 and cytochrome P450 1B1 and increased albumin secretion as comparedto an isolated 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 1.5 fold higher than an isolated 3-dimensionalliver spheroid cultured in Complete William's E medium alone, cytochromeP450 1A1 and cytochrome P450 1B1 activity that is at least 1.0 foldhigher and albumin secretion that is at least 1.9 fold higher ascompared to a cell cultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.1 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 1.9 fold higher andincreased albumin secretion that is at least 1.8 fold higher as comparedto a cell cultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.1 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 2.1 fold higher andalbumin secretion that is at least 2.0 fold higher as compared to a cellcultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.4 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 2.4 fold higher andalbumin secretion that is at least 2.1 fold higher as compared to a cellcultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.9 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 2.3 fold higher andalbumin secretion that is at least 2.6 fold higher as compared to a cellcultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.6 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 2.9 fold higher andalbumin secretion that is at least 2.5 fold higher as compared to a cellcultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.7 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 2.1 fold higher andalbumin secretion that is at least 3.3 fold higher as compared to a cellcultured in Complete William's E medium alone.

Liver cells grown in the cell culture medium/media can have an ATPcontent that is at least 2.7 fold higher, cytochrome P450 1A1 andcytochrome P450 1B1 activity that is at least 2.6 fold higher andalbumin secretion that is at least 3.1 fold higher as compared to a cellcultured in Complete William's E medium alone.

Methods of measuring ATP content, cytochrome P450 1A1 and cytochromeP450 1B1 activity and albumin secretion are described herein.

Suitably, liver cells grown in the cell culture medium/media have thesame number or an increased number of necrotic cells as compared tocells cultured in William's E medium alone.

Suitably, liver cells grown in the cell culture medium/media have anincreased number of apoptotic cells as compared to cells cultured inWilliam's E medium alone.

Suitably, liver cells grown in the cell culture medium/media havemodulated (for example, increased or decreased) levels of glutathione(GSH) as compared to cells cultured in William's E medium alone.

Suitably, liver cells grown in the cell culture medium/media haveincreased levels of oxidized glutathione (GSSG) as compared to cellscultured in William's E medium alone.

Suitably, the changes described herein are observed after 9 days ofculture.

Methods of measuring ATP content, cytochrome P450 1A1 and cytochromeP450 1B1 activity and albumin secretion are described in detail in theExamples. ATP content can be determined using the CellTiterGlo® assay(Promega, Dübendorf, Switzerland). Activity of CYP1A1/B1, CYP1A2, andCYP2B6 can be determined using the P450-Glo Assays (Promega, Dübendorf,Switzerland). Albumin secretion can be determined using the HumanAlbumin ELISA kit (Abcam).

Suitably, lung cells grown in the cell culture medium/media maintainviability, structural integrity and functional capabilities. Suitably,lung cells grown in the cell culture medium/media maintain the sameviability, structural integrity and functional capabilities as comparedto a lung cell cultured in Complete PneumaCult-ALI medium or CompleteB-ALI medium. Suitably, lung cells grown in the cell culturemedium/media are the same as lung cells cultured in CompletePneumaCult-ALI medium or Complete B-ALI medium.

The culture medium can be Complete PneumaCult-ALI medium which contains100% (v/v) Complete PneumaCult-ALI medium without any addition ordilution thereto.

The culture medium can be Complete B-ALI medium which contains 100%(v/v) Complete B-ALI medium without any addition or dilution thereto.

The culture medium can be a mixture comprising or consisting orconsisting essentially of Complete PneumaCult-ALI medium and CompleteWilliam's E medium. Complete PneumaCult-ALI medium is diluted withComplete William's E medium. In one embodiment, the mixture comprises orconsists of from 30% to 99.9% (v/v), from 40% to 99.9% (v/v), from 50%to 99.9% (v/v), from 60% to 99.9% (v/v), from 70% to 99.9% (v/v)Complete PneumaCult-ALI medium with the remaining volume being made upto 100% (v/v) with Complete William's E medium.

The culture medium can be a mixture comprising or consisting orconsisting essentially of a mixture comprising or consisting orconsisting essentially of Complete B-ALI medium and Complete William's Emedium. Complete B-ALI medium is diluted with Complete William's Emedium. In one embodiment, the mixture comprises or consists of 30% to99.9% (v/v), from 40% to 99.9% (v/v), from 50% to 99.9% (v/v), from 60%to 99.9% (v/v), from 70% to 99.9% (v/v) Complete B-ALI medium with theremaining volume being made up to 100% (v/v) with Complete William's Emedium.

(i) Complete B-ALI Medium

In one embodiment, the cell culture medium consists of complete B-ALImedium. In other words, the cell culture medium contains 100% (v/v)complete B-ALI medium with no added culture medium constituents. Inanother embodiment, the cell culture medium consists essentially ofcomplete B-ALI medium

Complete B-ALI Medium Promotes the Differentiation of Lung EpitheliumCells.

Complete B-ALI medium is prepared by combining together the contents ofthe B-ALI BulletKit (Lonza, catalogue number 193514), containing theB-ALI growth basal medium, B-ALI differentiation basal medium, and BALISingleQuots kit. The B-ALI BulletKit is made up of a Growth andDifferentiation Medium SingleQuots Kit, Growth Basal Medium andDifferentiation Basal Medium. It promotes full differentiation of lungepithelial cells.

According to this embodiment of the disclosure, a 3-dimensional liverspheroid cultured in complete B-ALI medium alone (ie. 100% (v/v)complete B-ALI medium) for 9 days has: (A) increased ATP content ascompared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone (ie. 100% (v/v) Complete William's E medium)for the same period of time; (B) the same or increased activity ofcytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; and (C) increased albumin secretion as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time. Suitably, the changes described herein are observed after 9days of culture.

Suitably, a 3-dimensional liver spheroid cultured in complete B-ALImedium alone (ie. 100% (v/v) complete B-ALI medium) for 9 days has: (A)a 1.9-fold increased ATP content as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time; (B) the sameactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; and (C) a 1.9-fold increased albumin secretion as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time (see Table 1). Suitably, the changes described herein areobserved after 9 days of culture.

In another embodiment, the cell culture medium comprises complete B-ALImedium with the proviso that a 3-dimensional liver spheroid cultured inthe cell culture medium comprising Complete B-ALI medium after 9 dayshas: (A) increased ATP content as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone; (B) the sameactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; and (C) increased albumin secretion as compared to a3-dimensional liver spheroid cultured in William's E medium alone.Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, the cell culture medium comprises complete B-ALI medium withthe proviso that a 3-dimensional liver spheroid cultured in the cellculture medium comprising complete B-ALI medium after 9 days has: (A) a1.9-fold increased ATP content as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time; (B) the sameactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; and (C) a 1.9-fold increased albumin secretion as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time (see Table 1).

Suitably, the isolated 3-dimensional liver spheroid when grown inculture has an increased number of apoptotic cells as compared to a3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has modulated (forexample, increased or decreased) levels of glutathione (GSH) as comparedto a 3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has increased levelsof oxidized glutathione (GSSG) as compared to a 3-dimensional liverspheroid cultured in William's E medium alone.

Suitably, the changes described herein are observed after 9 days ofculture.

(ii) Complete B-ALI Medium and Complete William's E Medium.

In one embodiment, the cell culture medium comprises or consists orconsists essentially of a mixture of Complete B-ALI medium and CompleteWilliam's E medium. Complete William's E medium is developed for theisolation and long term maintenance of adult rat liver epithelial cells.

Complete B-ALI medium is prepared by combining together the contents ofthe B-ALI BulletKit (Lonza, catalogue number 193514), containing theB-ALI growth basal medium, B-ALI differentiation basal medium, and BALISingleQuots kit. The B-ALI BulletKit is made up of a Growth andDifferentiation Medium SingleQuots Kit, Growth Basal Medium andDifferentiation Basal Medium. It promotes full differentiation of airwayepithelium.

Complete William's E medium is prepared by supplementing William's Emedium (ThermoFisher Scientific, catalogue number 12551032) with HepaRGMaintenance & Metabolism Supplement (ThermoFisher Scientific, cataloguenumber HPRG720) and GlutaMAX™ solution (ThermoFisher Scientific,catalogue number 35050061). William's E medium is described in Exp. CellRes. (1974) 89:139 and shown in Table 2. Complete B-ALI medium is mixedwith Complete William's E medium. The percentages of each medium thatare combined together can be varied. In one embodiment, the mixturecomprises, consists or consists essentially of at least 70% (v/v)Complete B-ALI medium with the remaining volume being made up to 100%(v/v) with Complete William's E medium. In one embodiment, the mixturecomprises, consists or consists essentially of 70%/30% (v/v) CompleteB-ALI medium/Complete William's E medium. In another embodiment, themixture comprises, consists or consists essentially of 75%/25% (v/v)Complete B-ALI medium/Complete William's E medium. In anotherembodiment, the mixture comprises, consists or consists essentially of80%/20% (v/v) Complete B-ALI medium/Complete William's E medium. Inanother embodiment, the mixture comprises, consists or consistsessentially of 85%/15% (v/v) Complete B-ALI medium/Complete William's Emedium. In another embodiment, the mixture comprises, consists orconsists essentially of 90%/10% (v/v) Complete B-ALI medium/CompleteWilliam's E medium. In another embodiment, the mixture comprises,consists or consists essentially of 95%/5% (v/v) Complete B-ALImedium/Complete William's E medium.

Suitably, when the mixture comprises, consists or consists essentiallyof 90%/10% (v/v) Complete B-ALI medium/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) increased ATP content as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone; (B) increasedactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; and (C) increased albumin secretion as compared to a3-dimensional liver spheroid cultured in William's E medium alone.Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 90%/10% (v/v) Complete B-ALI medium/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) a 2.1-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 1.9-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 1.8-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 80%/20% (v/v) Complete B-ALI medium/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) increased ATP content as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone; (B) increasedactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; and (C) increased albumin secretion as compared to a3-dimensional liver spheroid cultured in William's E medium alone.Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 80%/20% (v/v) Complete B-ALI medium/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) a 2.4-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 2.4-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 2.1-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 70%/30% (v/v) Complete B-ALI medium/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) increased ATP content as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone; (B) increasedactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; and (C) increased albumin secretion as compared to a3-dimensional liver spheroid cultured in William's E medium alone.Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 70%/30% (v/v) Complete B-ALI medium/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) a 2.1-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 2.1-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 2.0-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

As can be seen from the results summarised in Table 1, the mixture of80%/20% (v/v) complete B-ALI medium/complete William's E medium resultedin a combined 6.9-fold increase in ATP content, cytochrome P450 1A1 andcytochrome P450 1B1 activity and albumin secretion as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone. It is therefore fully excepted that further dilutions of thecomplete B-ALI medium in Complete William's E medium will result in acombined increase in ATP content, cytochrome P450 1A1 and cytochromeP450 1B1 activity as compared to a 3-dimensional liver spheroid culturedin Complete William's E medium alone. 60%/40% (v/v) complete B-ALImedium/Complete William's E medium, 50%/50% (v/v) complete B-ALImedium/Complete William's E medium, 40%/60% (v/v) complete B-ALImedium/Complete William's E medium, and 30%/70% (v/v) complete B-ALImedium/Complete William's E medium is disclosed.

Suitably, the isolated 3-dimensional liver spheroid when grown inculture has an increased number of apoptotic cells as compared to a3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has modulated (forexample, increased or decreased) levels of glutathione (GSH) as comparedto a 3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has increased levelsof oxidized glutathione (GSSG) as compared to a 3-dimensional liverspheroid cultured in William's E medium alone.

Suitably, the changes described herein are observed after 9 days ofculture.

(iii) Complete PneumaCult-ALI Medium.

In one embodiment, the cell culture medium consists of completePneumaCult-ALI medium. In other words, the cell culture medium contains100% (v/v) complete PneumaCult-ALI medium with no added culture mediumconstituents. In another embodiment, the cell culture medium consistsessentially of complete PneumaCult-ALI medium.

PneumaCult-ALI medium promotes the differentiation of lung epithelialcells.

Complete PneumaCult-ALI medium is prepared by mixing PneumaCult-ALIBasal Medium (StemCell Technologies, ref. 05002) with PneumaCult-ALI 10×Supplement (StemCell Technologies, ref. 05003), PneumaCult-ALIMaintenance Supplement (StemCell Technologies, ref. 05006),Hydrocortisone Stock Solution (StemCell Technologies, ref. 07925) and0.2% Heparin Sodium Salt in PBS (StemCell Technologies, ref. 37250).

According to this embodiment of the disclosure, a 3-dimensional liverspheroid cultured in complete PneumaCult-ALI medium alone (ie. 100%(v/v) complete PneumaCult-ALI medium) for 9 days has: (A) increased ATPcontent as compared to a 3-dimensional liver spheroid cultured inComplete William's E medium alone (ie. 100% (v/v) Complete William's Emedium) for the same period of time; (B) increased activity ofcytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; and (C) increased albumin secretion as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time. Suitably, the changes described herein are observed after 9days of culture.

Suitably, a 3-dimensional liver spheroid cultured in completePneumaCult-ALI medium alone (ie. 100% (v/v) complete PneumaCult-ALImedium) for 9 days has: (A) a 2.7-fold increased ATP content as comparedto a 3-dimensional liver spheroid cultured in Complete William's Emedium alone (ie. 100% (v/v) Complete William's E medium) for the sameperiod of time; (B) a 2.1-fold increased activity of cytochrome P450 1A1and cytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 3.3-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

In another embodiment, the cell culture medium comprises completePneumaCult-ALI medium with the proviso that a 3-dimensional liverspheroid cultured in the cell culture medium comprising completePneumaCult-ALI medium after 9 days has: (A) increased ATP content ascompared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone; (B) increased activity of cytochrome P450 1A1and cytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone; and (C) increased albuminsecretion as compared to a 3-dimensional liver spheroid cultured inWilliam's E medium alone. Suitably, the changes described herein areobserved after 9 days of culture.

Suitably, the cell culture medium comprises complete PneumaCult-ALImedium with the proviso that a 3-dimensional liver spheroid cultured inthe cell culture medium comprising complete PneumaCult-ALI medium after9 days has: (A) a 2.7-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 2.1-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 3.3-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, the isolated 3-dimensional liver spheroid when grown inculture has an increased number of apoptotic cells as compared to a3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has modulated (forexample, increased or decreased) levels of glutathione (GSH) as comparedto a 3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has increased levelsof oxidized glutathione (GSSG) as compared to a 3-dimensional liverspheroid cultured in William's E medium alone.

Suitably, the changes described herein are observed after 9 days ofculture.

(iv) Complete PneumaCult-ALI Medium and Complete William's E Medium

In one embodiment, the cell culture medium comprises or consists of amixture of Complete PneumaCult-ALI medium and Complete William's Emedium.

Complete PneumaCult-ALI medium is prepared by mixing PneumaCult-ALIBasal Medium (StemCell Technologies, catalogue number 05002) withPneumaCult-ALI 10× Supplement (StemCell Technologies, catalogue number05003), PneumaCult-ALI Maintenance Supplement (StemCell Technologies,catalogue number 05006), Hydrocortisone Stock Solution (StemCellTechnologies, catalogue number 07925) and 0.2% Heparin Sodium Salt inPBS (StemCell Technologies, catalogue number 37250).

Complete William's E medium is prepared by supplementing William's Emedium (ThermoFisher Scientific, catalogue number 12551032) with HepaRGMaintenance & Metabolism Supplement (ThermoFisher Scientific, cataloguenumber HPRG720) and GlutaMAX solution (ThermoFisher Scientific,catalogue number 35050061).

Complete PneumaCult-ALI medium is mixed with Complete William's Emedium. The percentages of each medium that are combined together can bevaried. In one embodiment, the mixture comprises, consists or consistsessentially of at least 70% (v/v) Complete PneumaCult-ALI medium withthe remaining volume being made up to 100% (v/v) with Complete William'sE medium.

In one embodiment, the mixture comprises, consists or consistsessentially of 70%/30% (v/v) Complete PneumaCult-ALI medium/CompleteWilliam's E medium. In another embodiment, the mixture comprises,consists or consists essentially of 75%/25% (v/v) CompletePneumaCult-ALI medium/Complete William's E medium. In anotherembodiment, the mixture comprises, consists or consists essentially of80%/20% (v/v) Complete PneumaCult-ALI medium/Complete William's Emedium. In another embodiment, the mixture comprises, consists orconsists essentially of 85%/15% (v/v) Complete PneumaCult-ALImedium/Complete William's E medium. In another embodiment, the mixturecomprises, consists or consists essentially of 90%/10% (v/v) CompletePneumaCult-ALI medium/Complete William's E medium. In anotherembodiment, the mixture comprises, consists or consists essentially of95%/5% (v/v) Complete PneumaCult-ALI medium/Complete William's E medium.

Suitably, when the mixture comprises, consists or consists essentiallyof 90%/10% (v/v) Complete PneumaCult-ALI medium/Complete William's Emedium a 3-dimensional liver spheroid cultured in the cell culturemedium after 9 days has: (A) increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; (B) increased activity of cytochrome P450 1A1 and cytochrome P4501B1 as compared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone; and (C) increased albumin secretion ascompared to a 3-dimensional liver spheroid cultured in William's Emedium alone. Suitably, the changes described herein are observed after9 days of culture.

Suitably, when the mixture comprises, consists or consists essentiallyof 90%/10% (v/v) Complete PneumaCult-ALI/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) a 2.9-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 2.3-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 2.6-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 80%/20% (v/v) Complete PneumaCult-ALI medium/Complete William's Emedium a 3-dimensional liver spheroid cultured in the cell culturemedium after 9 days has: (A) increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; (B) increased activity of cytochrome P450 1A1 and cytochrome P4501B1 as compared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone; and (C) increased albumin secretion ascompared to a 3-dimensional liver spheroid cultured in William's Emedium alone. Suitably, the changes described herein are observed after9 days of culture.

Suitably, when the mixture comprises, consists or consists essentiallyof 80%/20% (v/v) Complete PneumaCult-ALI/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) a 2.7-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 2.5-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 3.1-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, when the mixture comprises, consists or consists essentiallyof 70%/30% (v/v) Complete PneumaCult-ALI medium/Complete William's Emedium a 3-dimensional liver spheroid cultured in the cell culturemedium after 9 days has: (A) increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; (B) increased activity of cytochrome P450 1A1 and cytochrome P4501B1 as compared to a 3-dimensional liver spheroid cultured in CompleteWilliam's E medium alone; and (C) increased albumin secretion ascompared to a 3-dimensional liver spheroid cultured in William's Emedium alone. Suitably, the changes described herein are observed after9 days of culture.

Suitably, when the mixture comprises, consists or consists essentiallyof 70%/30% (v/v) Complete PneumaCult-ALI/Complete William's E medium a3-dimensional liver spheroid cultured in the cell culture medium after 9days has: (A) a 2.6-fold increased ATP content as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone (ie. 100% (v/v) Complete William's E medium) for the same periodof time; (B) a 2.9-fold increased activity of cytochrome P450 1A1 andcytochrome P450 1B1 as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone (ie. 100% (v/v) CompleteWilliam's E medium) for the same period of time; and (C) a 2.5-foldincreased albumin secretion as compared to a 3-dimensional liverspheroid cultured in complete William's E medium alone (ie. 100% (v/v)Complete William's E medium) for the same period of time (see Table 1).Suitably, the changes described herein are observed after 9 days ofculture.

Suitably, the isolated 3-dimensional liver spheroid when grown inculture has an increased number of apoptotic cells as compared to a3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has modulated (forexample, increased or decreased) levels of glutathione (GSH) as comparedto a 3-dimensional liver spheroid cultured in William's E medium alone.

Suitably, the isolated 3-dimensional liver spheroid has increased levelsof oxidized glutathione (GSSG) as compared to a 3-dimensional liverspheroid cultured in William's E medium alone.

Suitably, the changes described herein are observed after 9 days ofculture.

As can be seen from the results summarised in Table 1, the mixture of70%/30% (v/v) complete PneumaCult-ALI/Complete William's E mediumresulted in a combined 8-fold increase in ATP content, cytochrome P4501A1 and cytochrome P450 1B1 activity and albumin secretion as comparedto a 3-dimensional liver spheroid cultured in Complete William's Emedium alone. It is therefore fully excepted that further dilution ofthe complete PneumaCult-ALI in Complete William's E medium will resultin a combined increase in ATP content, cytochrome P450 1A1 andcytochrome P450 1B1 activity as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone. 60%/40% (v/v)complete PneumaCult-ALI/Complete William's E medium, 50%/50% (v/v)complete PneumaCult-ALI/Complete William's E medium, 40%/60% (v/v)complete PneumaCult-ALI/Complete William's E medium, and 30%/70% (v/v)complete PneumaCult-ALI/Complete William's E medium is disclosed.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture consisting of 80%/20% (v/v)complete PneumaCult-ALI/Complete William's E medium resulted in thelargest overall fold increase in ATP content, activity of cytochromeP450 1A1 and cytochrome P450 1B1 and albumin secretion of the3-dimensional liver spheroids. A cell culture medium mixture comprisingor consisting or consisting essentially of 80%/20% (v/v) completePneumaCult-ALI/Complete William's E medium is preferred for certainembodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture consisting or consistingessentially of 100% (v/v) complete PneumaCult-ALI medium resulted in thesecond largest overall fold increase in ATP content, activity ofcytochrome P450 1A1 and cytochrome P450 1B1 and albumin secretion of the3-dimensional liver spheroids. A cell culture medium consisting orconsisting essentially of 100% (v/v) complete PneumaCult-ALI medium ispreferred for certain embodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture comprising, consisting orconsisting essentially of 70%/30% (v/v) complete PneumaCult-ALI/CompleteWilliam's E medium resulted in the third largest overall fold increasein ATP content, activity of cytochrome P450 1A1 and cytochrome P450 1B1and albumin secretion of the 3-dimensional liver spheroids. A cellculture medium mixture comprising or consisting or consistingessentially of 70%/30% (v/v) complete PneumaCult-ALI/Complete William'sE medium is preferred for certain embodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture comprising, consisting orconsisting essentially of 90%/10% (v/v) complete PneumaCult-ALI/CompleteWilliam's E medium resulted in the fourth largest overall fold increasein ATP content, activity of cytochrome P450 1A1 and cytochrome P450 1B1and albumin secretion of the 3-dimensional liver spheroids. A cellculture medium mixture comprising or consisting or consistingessentially of 90%/10% (v/v) complete PneumaCult-ALI/Complete William'sE medium is preferred for certain embodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture comprising, consisting orconsisting essentially of 80%/20% (v/v) complete B-ALI medium/CompleteWilliam's E medium resulted in the fifth largest overall fold increasein ATP content, activity of cytochrome P450 1A1 and cytochrome P450 1B1and albumin secretion of the 3-dimensional liver spheroids. A cellculture medium mixture comprising or consisting or consistingessentially of 80%/20% (v/v) complete B-ALI medium/Complete William's Emedium is preferred for certain embodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture comprising, consisting orconsisting essentially of 70%/30% (v/v) complete B-ALI medium/CompleteWilliam's E medium resulted in the sixth largest overall fold increasein ATP content, activity of cytochrome P450 1A1 and cytochrome P450 1B1and albumin secretion of the 3-dimensional liver spheroids. A cellculture medium mixture comprising or consisting or consistingessentially of 70%/30% (v/v) complete B-ALI medium/Complete William's Emedium is preferred for certain embodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture comprising, consisting orconsisting essentially of 90%/10% (v/v) complete B-ALI medium/CompleteWilliam's E medium resulted in the seventh largest overall fold increasein ATP content, activity of cytochrome P450 1A1 and cytochrome P450 1B1and albumin secretion of the 3-dimensional liver spheroids. A cellculture medium mixture comprising or consisting or consistingessentially of 90%/10% (v/v) complete B-ALI medium/Complete William's Emedium is preferred for certain embodiments of the present disclosure.

Of the various media tested in the present disclosure for the culture of3-dimensional liver spheroids, the mixture comprising, consisting orconsisting essentially of 100% (v/v) complete B-ALI medium resulted inthe eighth largest overall fold increase in ATP content, activity ofcytochrome P450 1A1 and cytochrome P450 1B1 and albumin secretion of the3-dimensional liver spheroids. A cell culture medium mixture comprisingor consisting or consisting essentially of 100% (v/v) complete B-ALImedium is preferred for certain embodiments of the present disclosure.

A further aspect, relates to method for identifying a co-culture mediumthat can be used for the co-culture of the lung cells and liver cellsdescribed herein, comprising: (a) providing a culture medium comprisingComplete PneumaCult-ALI medium or Complete William's E medium; (b)mixing the Complete PneumaCult-ALI medium or Complete William's E mediumwith a culture medium this is optimised for or specific for the cultureof liver cells to provide a cell culture medium mixture; (c) adding aco-culture of lung cells and liver cells to the cell culture mediummixture: and (d) identifying a cell culture medium mixture in which theliver cell has: increased ATP content as compared to a liver cellcultured in Complete William's E medium alone; the same or increasedactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to aliver cell cultured in Complete William's E medium alone; and increasedalbumin secretion as compared to a liver cell cultured in William's Emedium alone and the lung cell retains its characteristics. Otherproperties of the liver cell are described herein.

A further aspect, relates to a co-culture medium that can be used forthe co-culture of lung cells and liver cells obtained or obtainable bythis process, wherein a liver cell cultured in the co-culture mediumhas: increased ATP content as compared to a liver cell cultured inComplete William's E medium alone; the same or increased activity ofcytochrome P450 1A1 and cytochrome P450 1B1 as compared to a liver cellcultured in Complete William's E medium alone; and increased albuminsecretion as compared to a liver cell cultured in William's E mediumalone and the lung cell retains its characteristics. Other properties ofthe liver cell are described herein.

3-Dimensional Organ Culture Systems

3-dimensional organ culture systems, especially those in miniaturisedform, are of use in the present disclosure as they allow the study ofhow organs function. Response to certain stimuli, response to one ormore chemical compounds or compositions and pharmacokinetic behaviour ofsuch compounds or compositions can be studied, for example, in screeningassays as described herein. Miniaturised 3-dimensional organ culturesystems, also known as organ on-a-chip, are of particular interest asthey allow the combined study of groups of organs, that is, the study ofat least 3-dimensional lung and liver tissues. This allows thecomplexity of interaction between lung and liver tissues to bereproduced. The 3-dimensional culture system of the present disclosurewhich takes into account lung and liver organs and allows dynamicculture of these multiple organs is therefore highly advantageous. Themajority of 3-dimensional organ culture systems are organotypic, whichmeans that they seek to reproduce major functions of an organ or organsystem. A miniaturised fluidic system interconnecting the lung and livertissues is also described.

Suitably, the organ-on-a-chip is a microfluidic device that has at leastone physiological function of at least one tissue type—such as lung orliver, or more suitably has at least one physiological function of atleast two different tissue types—such as lung and liver. Theorgan-on-a-chip can be of any living tissue or organ from any organismincluding mammals, non-mammals, and animals.

The organ-on-a-chip will generally comprise at least one microfluidicchannel disposed therein. The exact dimension of these channels willdiffer based on the function and/or dimensions of the chip. The at leastone microfluidic channel will generally function to provide andreplenish nutrients to the biological material on the chip.

In one aspect, the 3-dimensional multi-organ culture system comprises:(a) a first organ growth section adapted to culture or submerge a first3-dimensional cell type—such as liver—in a culture medium; (b) a secondorgan growth section adapted to culture a second 3-dimensional celltype—such as lung—at an air liquid interface, the second 3-dimensionalcell type being a cell type that is different than the first3-dimensional cell type; and (c) a culture medium reservoir connectingthe first organ cavity and the second organ cavity to allow for the flowof culture medium there between.

The first organ growth section can comprise a first organ cavity orreceptacle or vessel or container or containment means.

The second organ growth section can comprise a second organ cavity orreceptacle or vessel or container or containment means.

The reservoir can be provided by a microfluidic channel. Suitably, thefirst organ growth section—such as the first organ cavity—and the secondorgan growth section—such as the second organ cavity—contain the sameculture medium—such as culture medium comprising or consisting orconsisting essentially of: (a) Complete PneumaCult-ALI medium; or (b)Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium or a variation thereof as described herein.

In addition to the cell types described herein, the chip can compriseadditional cell types to create a multi-organ chip.

The person skilled in the art is able to design a chip with the optimumnumber and/or dimension of channels required to achieve a particularapplication.

The chip can comprise a fluid control element to modulate fluidflow—such as a pump or a valve microchannel to control microcirculationwithin the chip.

Cells and tissues on the chip can be oxygenated using, for example, gasexchange membranes.

The chip can further comprise one or more sensors for monitoring avariable and/or a response of a cell to its surrounding conditions.

The chip can be fabricated from any suitable material that will befamiliar to the person skilled in the art. Examples of such materials,suitably, biocompatible materials, are silicon, polyurethanes, glass,plastic, polymethylmethacrylate (PMMA), polycarbonate,polytetrafluoroethylene (TEFLON™), polyvinylchloride (PVC),polydimethylsiloxane (PDMS), and rubber.

The chip can also comprise further components, as required, such asoxygenators, pumps, valves, gas-exchangers and bubble traps.

Various kinds of organ-on-a-chip are described in the art—see forexample, Lab Chip (2015) 15, 2688-2699 and Lab. Chip (2013) 13, 3538.

The function of tissue or organs on the chip can be assessed usingvarious methods, some of which are described herein. For example thetissue or organs can be monitored morphologically using imaginingtechniques. The functionality of a lung chip can be monitored bymeasuring permeability barrier function, surfactant production, andmeasuring responses to cytokines, for example. The functionality of aliver chip can be monitored using various assays, at least some of whichare described herein. Such assays can include transporter function,cytochrome P450 expression and albumin secretion.

Liver Based 3-Dimensional Culture

The liver plays a central role in detoxification, metabolism ofcarbohydrates, lipids and proteins as well as biotransformation ofendogenous and exogenous substances. Liver functionality is closelylinked to the assembly of highly specialised cells, the majority ofwhich are hepatocytes, embedded in a complex 3-dimensional structuremade up of so-called lobules. Biotransformation of compounds usuallyresults in non-toxic and more soluble metabolites, however,occasionally, more toxic metabolites may be formed causinghepatotoxicity.

It is possible to culture 3-dimensional liver cells using variousmethods that are well documented in the art, including the use ofcollagen sandwich cultures, membrane bioreactors, stirrer bioreactors,hanging drop, polystyrene scaffold culture and using a microfluidicdevice.

Hepatocytes can be changed into 3-dimensions via various methods,including the use of sandwich culture, solid scaffold materials—such aspolystyrene scaffolds, hydrogels—such as collagen type-I, orself-assembling of hepatocytes into spheroids.

Whilst the use of freshly isolated primary human hepatocytes limited maybe the preferred lung cell type of the present disclosure, theiravailability is limited. Other choices of human liver cell lines includeHepG2 and Hep2/C3A. A particularly suitable cell source is the HepaRGcell line. Other sources of human hepatocytes are human embryonic stemcell (hESC) derived hepatocytes and hepatocytes derived from inducedpluripotent stem cells (iPSC).

3-dimensional liver spheroids are of particular use in the presentdisclosure. They can be produced in scaffold free systems in multiwellplates by the self-assembling of hepatocytes into aggregates or instirrer bioreactors. Liver spheroids form liver like structures withinand are viable for long periods of time exhibiting good functionalitymaking them well suited for high throughput applications and for use onchips.

Lung Based 3-Dimensional Culture

As the morphology of the respiratory tract changes from the upper to thelower airways, many different cell culture models have been establishedusing primary cells or cell lines and are contemplated for use in thepresent disclosure. The choice of exactly which cell or cell line to usewill depend on the area of interest of the respiratory tract for a givenstudy.

Lung-on-a-chip models are able to reproduce the structure and functionof the living lung. In one example of such a model, a microfluidicsystem containing two closely apposed microchannels separated by amembrane can be fabricated. The membrane can be coated withextracellular matrix, and human alveolar epithelial cells and humanpulmonary microvascular endothelial cells can be cultured on oppositesides of the membrane. Once the cells are grown to confluence, air isintroduced into the epithelial compartment to create an air-liquidinterface to mimic the lining of the alveolar air space.

Since the lung surface is exposed to air, the cell model is cultured atthe air-liquid interface to mimic the lung more realistically.

Screening

The effect of one or more agents on 3-dimensional cells, tissues ororgans can be determined using the methods described herein. In oneaspect, there is described an in vitro method for assessing the responseof a 3-dimensional cell, tissue or organ to an agent, the methodcomprising: (i) contacting a 3-dimensional cell or a co-culture or a3-dimensional organ culture system or a 3-dimensional multi-organculture system with at least one agent; and (ii) measuring one or moreresponses after contact with the at least one agent; wherein adifference in the one or more responses before and after contact withthe at least one agent is indicative that the agent modulates theresponse of the cell, tissue or organ.

There is also described an in vitro method for assessing the response ofa 3-dimensional liver cell, tissue or organ and a 3-dimensional lungcell, tissue or organ to an agent, the method comprising: (i) contactinga co-culture, or a 3-dimensional organ culture system, or a3-dimensional multi-organ culture system with at least one agent; and(ii) measuring one or more responses after contact with the at least oneagent; wherein a difference in the one or more responses before andafter contact with the at least one agent is indicative that the agentmodulates the response of the cell, tissue or organ.

Suitably, the penetration of at least one agent into the 3-dimensionallung cell, tissue or organ is measured or determined. Suitably, thebio-activation of the at least one agent in the 3-dimensional livercell, tissue or organ is measured or determined. These steps can becarried out simultaneously or subsequently to each other.

The effect of one or more agents on 3-dimensional lung cell, tissue ororgan can be determined using the methods described herein. The effectof one or more agents on 3-dimensional liver cell, tissue or organ canbe determined using the methods described herein. The effect of one ormore agents on 3-dimensional lung cell, tissue or organ and3-dimensional liver cell, tissue or organ can be determined using themethods described herein. The effect of one or more agents on thepenetration of an agent—such as an aerosol—into 3-dimensional lung cell,tissue or organ and its further bio-activation in liver cell, tissue ororgan can be determined using the methods described herein. The agentcan include, but is not limited to, a drug, a toxin, a pathogen, anantigen, an antibody, and an aerosol etc. The agent can be added to the3-dimensional culture system described herein and its effect on the3-dimensional cultured cell, tissue or organ can be monitored ordetermined. Examples of the effects that can be measured includeconsumption of oxygen, production of carbon dioxide, cell viability,expression of a protein, the activity of an enzyme, penetration,permeability barrier function, surfactant production, response tocytokines, transporter function, cytochrome P450 expression, albuminsecretion and the like.

A plurality of assays may be run in parallel with differentconcentrations of the agent to obtain a differential response to thevarious concentrations. As known in the art, the process of determiningthe effective concentration of an agent typically uses a range ofconcentrations resulting from 1:10, or other log scale, dilutions. Theconcentrations may be further refined with a second series of dilutions,if necessary. Typically, one of these concentrations serves as anegative control.

An agent (for example, a test compound) may be any compound of interestand includes small organic compounds, polypeptides, peptides, highermolecular weight carbohydrates, polynucleotides, fatty acids and lipids,aerosol or one or more components of an aerosol and the like. Testcompounds may be screened individually or in sets or combinatoriallibraries of compounds. Test compounds can be obtained from a widevariety of sources including libraries of synthetic or naturalcompounds. Libraries of natural compounds in the form of bacterial,fungal, plant and animal extracts can be used. Natural or syntheticallyproduced libraries and compounds that are modified through conventionalchemical, physical and biochemical means may be used to producecombinatorial libraries. Known pharmacological agents may be subjectedto directed or random chemical modifications, such as acylation,alkylation, esterification, acidification to produce structuralanalogues for screening. When screening using a combinatorial library, alarge library of chemically similar or diverse molecules can bescreened. In combinatorial screening, the number of hits discovered isproportional to the number of molecules tested. The large numbers ofcompounds, which may reach thousands of compounds tested per day, can bescreened, in which laboratory automation and robotics may be applied.Many examples of methods for the synthesis of molecular libraries can befound in the art. A small organic compound includes a compound ofmolecular weight less than about 5000, usually less than about 2500,usually, less than about 2000, more usually, less than about 1500,suitably about 100 to about 1000. The small organic compounds may beeither biological or synthetic organic compounds. The atoms present inthe small organic compound are generally in the group comprising carbon,hydrogen, oxygen, and nitrogen and may include halogens, boron,phosphorus, selenium and sulphur if in a pharmaceutically acceptableform. Generally, oxygen, nitrogen, sulphur or phosphorus, if present,are bound to carbon or one or more of each other or to hydrogen to formvarious functional groups such as, for example, carboxylic acids,alcohols, thiols, carboxamides, carbamates, carboxylic acid esters,amides, ethers, thioethers, thioesters, phosphates, phosphonates,olefins, ketones, amines, aldehydes, and the like. The small organiccompounds, as the term is used herein, also include small peptides,small oligonucleotides, small polysaccharides, fatty acids, lipids, andthe like having a molecular weight less than about 5000.

Examples of pharmaceutical agents are described in The PharmacologicalBasis of Therapeutics, Goodman and Gilman, McGraw-Hill, New York, N.Y.,(1996), Ninth edition. The agent can be a toxin.

Test compounds in solution and solid samples that can be dissolved in asuitable solvent can be assayed. Test compounds in gaseous form can alsobe assayed by exposing samples to the gas for a period of time. Samplesof interest include environmental samples, biological samples,manufacturing samples, libraries of compounds and synthetic andnaturally occurring compounds.

Polypeptides that have a molecular weight of at least about 5,000, moreusually at least about 10,000 can be screened. The test polypeptideswill generally be from about 5,000 to about 5,000,000 or more molecularweight, more usually from about 20,000 to about 1,000,000 molecularweight. A wide variety of polypeptides may be considered such as afamily of polypeptides having similar structural features, polypeptideshaving particular biological functions, polypeptides related to specificmicroorganisms, particularly disease causing microorganisms. Suchpolypeptides include cytokines or interleukins, enzymes, protamines,histones, albumins, immunoglobulins, scleropolypeptides,phosphopolypeptides, mucopolypeptides, chromopolypeptides,lipopolypeptides, nucleopolypeptides, glycopolypeptides, T-cellreceptors, proteoglycans, somatotropin, prolactin, insulin, pepsin,polypeptides found in human plasma, blood clotting factors, blood typingfactors, polypeptide hormones, cancer antigens, tissue specificantigens, peptide hormones, nutritional markers, tissue specificantigens, and synthetic peptides, which may or may not be glycated.

Polynucleotides can be screened. The test polynucleotide may be anatural compound or a synthetic compound. Polynucleotides includeoligonucleotides and are comprised of natural nucleotides such asribonucleotides and deoxyribonucleotides and their derivatives althoughunnatural nucleotide mimetics such as 2′-modified nucleosides, peptidenucleic acids and oligomeric nucleoside phosphonates are alsocontemplated. The higher molecular weight polynucleotides can have fromabout 20 to about 5,000,000 or more nucleotides.

One or more variables that can be measured include quantifiable elementsof cells, subcellular material, subcellular components, or cellularproducts, particularly elements that can be accurately measured in ahigh throughput assay system. An output can be a feature, condition,state or function of any cell, cellular component or cellular productincluding viability, respiration, metabolism, cell surface determinant,receptor, protein or conformational or posttranslational modificationthereof, lipid, carbohydrate, organic or inorganic molecule, DNA, RNAand the like or a portion derived from such a cell component. While thevariable(s) can provide a quantitative readout, in some instances asemi-quantitative or qualitative result can be obtained. Readoutvariables may include a single value, or a mean value, or a median valueor a variance thereof, for example.

Various methods can be used to measure the variable(s) to determine thecell, tissue or organ's response to an agent/test compound. Formeasuring the amount of a molecule that is present, one method is tolabel the molecule with a detectable moiety, which may be fluorescent,luminescent, radioactive, enzymatically active, and the like.Fluorescent and luminescent moieties are available for labelling abiomolecule, structure, or cell type. Immunofluorescent moieties can bedirected to bind not only to specific proteins but also specificconformations, cleavage products, or site modifications likephosphorylation. Individual peptides and proteins can be engineered toauto-fluoresce. Immunoassay techniques—such as immunohistochemistry,radioimmunoassay (RIA), or enzyme linked immunosorbance assay (ELISA)and related non-enzymatic techniques can be used. These techniquesutilize specific antibodies as reporter molecules which are particularlyuseful due to their high degree of specificity for attaching to a singlemolecular target. Cell-based ELISA or related non-enzymatic orfluorescence-based methods enable measurement of cell surfaceparameters.

The results of screening assays may be compared to results obtained fromreference compounds, concentration curves, controls and the like. Theagent can be an aerosol—such as smoke or an aerosol derived from smoke.

Aerosol

One embodiment relates to studying the penetration of an agent—such asan aerosol—into the 3-dimensional lung cell, tissue or organ describedherein. Another embodiment relates to studying the penetration of anagent—such as an aerosol—into the 3-dimensional lung cell, tissue ororgan and its further bio-activation in liver cell, tissue or organ. Inparticular, this can be carried out on the 3-dimensional organ culturesystems described herein.

The aerosol may be derived or generated by an aerosol forming device.Smoking articles and smokable articles are types of aerosol formingdevices. Examples of smoking articles or smokable articles include butare not limited to cigarettes, cigarillos, and cigars. In certainaerosol forming devices, rather than combustion, a tobacco compositionor another aerosol forming material is heated by one or more electricalheating elements to produce an aerosol. In another type of heatedaerosol forming device, an aerosol is produced by the transfer of heatfrom a combustible fuel element or heat source to a physically separateaerosol forming material, which may be located within, around ordownstream of the heat source. Typically in heated smoking articles, anaerosol is generated by the transfer of heat from a heat source to aphysically separate aerosol-forming substrate or material, which may belocated within, around or downstream of the heat source. During smoking,volatile compounds are released from the aerosol-forming material byheat transfer from the heat source and entrained in air drawn throughthe smoking article. As the released compounds cool, they condense toform an aerosol that is inhaled by the user. As used herein, the term‘aerosol forming material’ is used to describe a material capable ofreleasing upon heating volatile compounds, which can form an aerosol.The aerosol forming material may be plant-based. Examples of aerosolforming materials include but are not limited to tobacco compositions,tobaccos, tobacco extract, cut tobacco, cut filler, cured tobacco,expanded tobacco, homogenized tobacco, reconstituted tobacco, and pipetobaccos. The aerosol-forming material may alternatively comprise anon-plant-based-containing material.

The aerosol can be in the form of smoke. As used herein, the term‘smoke’ is used to describe a type of aerosol that is produced bysmoking articles, such as cigarettes, or by combusting an aerosolforming material. Smoke includes various agents, which can be providedas individual compounds for study if required. Examples of such agentsinclude nicotine-free dry particulate matter, carbon monoxide,formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde,crotonaldehyde, methyl-ethly ketone, butyraldehyde, benzo[a]pyrene,phenol, m-cresol, o-cresol, p-cresol, catechol, resorcinol,hydroquinone, 1,3-butadiene, isoprene, acrylonitrile, benzene, toluene,pyridine, quinoline, styrene, N′-nitrosonornicotine (NNN),N′-nitrosoanatabine (NAT), N′-nitrosoanabasine (NAB),4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK),1-aminonaphthalene, 2-aminonaphthalene, 3-aminobiphenyl,4-aminobiphenyl, nitrogen monoxide (NO), nitrous oxide (NOx), cyanhydricacid, ammonia, arsenic, cadmium, chrome, lead, nickel, selenium andmercury.

The 3-dimensional organ culture system described herein can be exposedfor various amounts of time to smoke. Smoke can be delivered using aVitrocell smoking robot as described in Am. J. Physiol. Lung Cell MolPhysiol 304: L489-L503 (2013). A defined number of puffs per cigaretteand a defined number of puffs per minute of exposure can be used and thenumber of cigarettes varied to adjust to the exposure times. Referencecigarettes—such as the reference cigarettes 3R4F can be used as thesource of the smoke and smoked on the smoking robot in basic conformitywith the International Organization for Standardization smoking regimen(ISO 2000). After exposure, the 3-dimensional organ culture system canoptionally be incubated with fresh culture medium before analysis.

Kits

Kits are also contemplated. The culture medium or culture mediadescribed herein can be filled into one or more suitable containers. Asuitable container can be a sterilisable flask or a sterilisable bottleor a sterilisable beaker comprising a top—such as a sealable orre-sealable top. Therefore, the present disclosure also relates to acontainer comprising the culture medium described herein. The presentdisclosure also relates to multiple containers comprising the culturemedia described herein. In addition, the present disclosure relates to apackage or kit comprising single or multiple flasks or bottlescomprising the culture media optionally together with instructions forpreparing same. Optionally one or more of the cell types describedherein can be included in the package or kit. Optionally one or morereference cigarettes can be included in the package or kit. Instructionsfor use can also be included.

Further Aspects

Further aspects of the disclosure are presented in the followingnumbered paragraphs:

1. An isolated 3-dimensional liver spheroid, wherein the spheroid has:increased ATP content as compared to a 3-dimensional liver spheroidcultured in Complete William's E medium alone; the same or increasedactivity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; and increased albumin secretion as compared to a 3-dimensionalliver spheroid cultured in William's E medium alone.

2. An isolated 3-dimensional liver spheroid for use in a 3-dimensionalmulti-organ culture system obtained or obtainable by a processcomprising: culturing a 3-dimensional liver spheroid in a cell culturemedium comprising or consisting or consisting essentially of either: (a)Complete PneumaCult-ALI medium; or (b) Complete B-ALI medium; or (c)Complete PneumaCult-ALI medium and Complete William's E medium, or (d)Complete B-ALI medium and Complete William's E medium, for a period oftime that is sufficient to obtain a 3-dimensional liver spheroid inwhich: ATP content is increased as compared to a 3-dimensional liverspheroid cultured in Complete William's E medium alone; cytochrome P4501A1 and cytochrome P450 1B1 activity is increased as compared to a3-dimensional liver spheroid cultured in Complete William's E mediumalone; and albumin secretion is increased as compared to a 3-dimensionalliver spheroid cultured in Complete William's E medium alone.

3. The isolated 3-dimensional liver spheroid according to paragraph 1 orparagraph 2 wherein the spheroid is or is derived from a human hepaticprogenitor cell line, suitably, wherein the spheroid is or is derivedfrom a HepaRG cell.

4. The isolated 3-dimensional liver spheroid according to paragraph 1 orparagraph 3, wherein the spheroid is cultured in a cell culture mediumcomprising or consisting or consisting essentially of either: (a)Complete PneumaCult-ALI medium; or (b) Complete B-ALI medium; (c)Complete PneumaCult-ALI medium and Complete William's E medium, or (d)Complete B-ALI medium and Complete William's E medium.

5. A co-culture comprising the 3-dimensional liver spheroid according toany of the preceding paragraphs and a 3-dimensional lung epithelialcell.

6. The co-culture according to paragraph 5, wherein the co-culture ismaintained in a cell culture medium comprising or consisting orconsisting essentially of either: (a) Complete PneumaCult-ALI medium; or(b) Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium.

7. A 3-dimensional organ culture system comprising the isolated3-dimensional liver spheroid according to any of paragraphs 1 to 4.

8. A 3-dimensional multi-organ culture system comprising the isolated3-dimensional liver spheroid according to any of paragraphs 1 to 4 andfurther comprising at least one other 3-dimensional cell type, orcomprising the co-culture according to paragraph 5 or paragraph 6.

9. The 3-dimensional organ culture system according to paragraph 7 orthe 3-dimensional multi-organ culture system according to paragraph 8,wherein the 3-dimensional liver spheroid is submerged in culture mediumcontained on the culture system.

10. The 3-dimensional multi-organ culture system according to paragraph8 or 9, further comprising a 3-dimensional lung epithelial cell,suitably, wherein the 3-dimensional lung epithelial cell is at an airliquid interface on the 3-dimensional multi-organ culture system.

11. A 3-dimensional multi-organ culture system comprising: (a) a firstorgan growth section comprising a first organ cavity adapted to submergea first 3-dimensional cell type in a culture medium; (b) a second organgrowth section comprising a second organ cavity adapted to culture asecond 3-dimensional cell type at an air liquid interface, the second3-dimensional cell type being a cell type that is different than thefirst 3-dimensional cell type; and (c) a culture medium reservoirconnecting the first organ cavity and the second organ cavity to allowfor the flow of culture medium there between.

12. The 3-dimensional multi-organ culture system according to paragraph11, wherein the first organ cavity and second organ cavity contain thesame culture medium.

13. The 3-dimensional multi-organ culture system according to paragraph11 or paragraph 12, comprising the co-culture according to paragraph 5or paragraph 6.

14. The 3-dimensional organ culture system according to paragraph 7 orthe 3-dimensional multi-organ culture system according to any ofparagraphs 8 to 13, wherein said system is miniaturised.

15. The 3-dimensional organ culture system according to paragraph 7 or14, or the 3-dimensional multi-organ culture system according to any ofparagraphs 8 to 14, wherein said system comprises or is a microfluidicdevice, suitably, wherein said system is an organ-on-a-chip.

16. A cell culture medium comprising or consisting or consistingessentially of: (a) a mixture of Complete PneumaCult-ALI medium andComplete William's E medium; or (b) a mixture of Complete B-ALI mediumand Complete William's E medium.

17. The cell culture medium according to paragraph 16, furthercomprising the 3-dimensional liver spheroid according to any ofparagraphs 1 to 4 or the co-culture according to paragraph 5 orparagraph 6.

18. A 3-dimensional multi-organ culture system comprising a culturemedium, said culture medium selected from the group consisting of aculture medium comprising or consisting or consisting essentially ofeither: (a) Complete PneumaCult-ALI medium; or (b) Complete B-ALImedium; or (c) Complete PneumaCult-ALI medium and Complete William's Emedium, or (d) Complete B-ALI medium and Complete William's E medium ora combination of two or more thereof.

19. A method of preparing a 3-dimensional liver spheroid for use in a3-dimensional organ culture system comprising: (i) providing a3-dimensional liver spheroid; (ii) contacting the 3-dimensional liverspheroid with a culture medium comprising or consisting or consistingessentially of either: (a) Complete PneumaCult-ALI medium; or (b)Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium; and (iii) obtaining a 3-dimensional liver spheroidfor use in a 3-dimensional organ culture system.

20. A method of preparing a co-culture comprising or consisting orconsisting essentially of a 3-dimensional liver spheroid and a3-dimensional lung epithelial cell for use in a 3-dimensionalmulti-organ culture system comprising: (i) providing a 3-dimensionalliver spheroid and a 3-dimensional lung epithelial cell; (ii) contactingthe 3-dimensional liver spheroid and the 3-dimensional lung epithelialcell with a culture medium comprising or consisting or consistingessentially of either: (a) Complete PneumaCult-ALI medium; or (b)Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium; and (iii) obtaining a co-culture of a 3-dimensionalliver spheroid and a 3-dimensional lung epithelial cell.

21. An in vitro method for assessing the response of a 3-dimensionalliver spheroid to an agent, the method comprising: (i) contacting the3-dimensional liver spheroid according to any of paragraphs 1 to 4 orthe co-culture according to paragraph 5 or 6 or the 3-dimensional organculture system according to paragraph 7, 14 or 15, or the 3-dimensionalmulti-organ culture system according to any of paragraphs 8 to 15 withat least one agent; and (ii) measuring one or more responses of the3-dimensional liver spheroid or the co-culture or the 3-dimensionalorgan culture system or the 3-dimensional multi-organ culture systemafter contact with the at least one agent; wherein a difference in theone or more responses before and after contact with the at least oneagent is indicative that the agent modulates the response of the cell.

22. An in vitro method for assessing the response of a 3-dimensionalliver spheroid and a 3-dimensional lung epithelial cell to an agent, themethod comprising: (i) contacting the co-culture according to paragraph5 or 6 or the 3-dimensional organ culture system according to paragraph7, 14 or 15, or the 3-dimensional multi-organ culture system accordingto any of paragraphs 8 to 15 with at least one agent; and (ii) measuringone or more responses of the co-culture or the 3-dimensional organculture system or the 3-dimensional multi-organ culture system aftercontact with the at least one agent; wherein a difference in the one ormore responses before and after contact with the at least one agent isindicative that the agent modulates the response of the cell.

23. The in vitro method according to paragraph 22, wherein step (ii)comprises measuring the penetration of the at least one agent into the3-dimensional lung epithelial cell.

24. The in vitro method according to paragraph 23, comprising thefurther step of: (iii) measuring the bio-activation of the at least oneagent in the 3-dimensional liver spheroid; wherein the measurements insteps (ii) and (iii) are carried out simultaneously or wherein themeasurement in step (iii) is carried out after the measurement in step(ii).

25. The in vitro method according to any of paragraphs 22 to 24, whereinthe agent is an aerosol, suitably, wherein the aerosol is or is derivedfrom smoke, suitably, cigarette smoke.

26. Use of a cell culture medium comprising or consisting or consistingessentially of either: (a) Complete PneumaCult-ALI medium; or (b)Complete B-ALI medium; or (c) Complete PneumaCult-ALI medium andComplete William's E medium, or (d) Complete B-ALI medium and CompleteWilliam's E medium, for culturing a 3-dimensional liver spheroid or a3-dimensional lung epithelial cell or for co-culturing a 3-dimensionalliver spheroid and a 3-dimensional lung epithelial cell.

27. Use of the 3-dimensional organ culture system according to paragraph7, 14 or 15, or the 3-dimensional multi-organ culture system accordingto any of paragraphs 8 to 15 for toxicity testing or for drug discoveryor for determining the penetration of an agent into lung cells and/orfor determining the bio-activation of an agent in liver cells, suitably,wherein the agent is an aerosol.

Although illustrative embodiments of the invention have been disclosedin detail herein, with reference to the accompanying drawings, it isunderstood that the invention is not limited to the precise embodimentand that various changes and modifications can be effected therein byone skilled in the art without departing from the scope of the inventionas defined by the appended claims and their equivalents.

The invention is further described in the Examples below, which areprovided to describe the invention in further detail. These examples,which set forth a preferred mode presently contemplated for carrying outthe invention, are intended to illustrate and not to limit theinvention.

EXAMPLES Example 1

Preparation of Bronchial Organotypic Cultures

These are prepared according to the protocol from Lonza (Basel,Switzerland) entitled Clonetics™ B-ALI™ air-liquid interface medium.Briefly, normal human bronchial epithelial cells (NHBEC) are expanded inComplete B-ALI medium at 37° C. in 5% CO2 (90% relative humidity) untila confluency of approx. 80%. Cells are trypsinized, washed andresuspended. 35,000 cells are seeded onto collagen-I-coated Transwell®inserts (Corning®, Root Langenbold, Switzerland), and inserts are placedin multiwell plates prefilled with Complete B-ALI medium (Lonza) andincubated for 3 days. Apical medium is then removed, and basal medium isreplaced with Complete B-ALI medium. Air-lifted inserts are returned tothe incubator, and medium is replaced every 2 to 3 days. Additionally,apical washes are performed once a week during the maturation phase.Cultures are used once mature, typically at 4 weeks following theair-lift. Morphological assessment, measurements of ATP content, apicalATP secretion and CYP1A1/B1 activity are performed weekly, for up to 4weeks after maturation (see FIG. 1). With the exception of insertsdedicated to histological evaluation and ATP content measurements, allinserts are re-used throughout the time course.

Example 2

Preparation of Liver Spheroids

Liver spheroids are prepared as described in the GravityTRAP™ ULA Platemanual from InSphero. Briefly, HepaRG cells are first thawed at 37° C.for 2 minutes and then mixed into 9 ml of pre-warmed William's E medium(ThermoFisher Scientific, ref. 12551032) supplemented with Thaw, Plate &General Purpose supplement (ThermoFisher Scientific, ref. HPRG770) andGlutaMAX solution (ThermoFisher Scientific, ref. 35050061). Cells arethen centrifuged for 2 minutes at 400×g before medium is replaced withfresh William's E medium with the same supplements as described above.About 5000 cells are then distributed per wells of a Corning® spheroidmicroplate (ref. 4520). 5 days later, medium is replaced with freshWilliam's E medium (ThermoFisher Scientific, ref. 12551032) supplementedwith HepaRG Maintenance & Metabolism Supplement (ThermoFisherScientific, ref. HPRG720) and GlutaMAX solution (ThermoFisherScientific, ref. 35050061). One week later, spheroids are mature andready to be used for the experiments.

Example 3

Determining Morphology of Bronchial Organotypic Cultures and LiverSpheroids

Morphology of bronchial organotypic cultures is evaluated followingfixation and paraffin embedding, sectioning and staining withhematoxylin and eosin (H&E) and Alcian blue as previously described inToxicol Sci. 2015 September; 147(1):207-21.

Liver spheroid morphology is assessed following immunostaining. Inbrief, liver spheroids are fixed in 4% fresh paraformaldehyde overnight.Following blocking in 1% Triton X-100/0.2% fish skin gelatin (FSG),spheroids are stained with mouse anti-cytokeratin 19 (1/500, Abcam,Cambridge, UK) diluted in PBS with 0.1% FSG for 24 hours. The primaryantibody is visualized using a FITC-labeled goat anti-mouse antibody(1/500, Abcam). Spheroids are then mounted using ProLong Diamondantifade with DAPI (Thermo Fisher) and evaluated by high-content imagingon the Cellinsight™ CX7 platform (Thermo Fisher).

Example 4

Determining ATP Content of Bronchial Organotypic Cultures and LiverSpheroids

This is determined using the CellTiterGlo® 3D cell viability assay(Promega, Dübendorf, Switzerland) according to the manufacturer'srecommendations.

For measurements in bronchial cultures, undiluted CellTiterGlo® reagentis directly added to the cultures, yielding intracellular ATP content.

For analysis of liver spheroids, CellTiterGlo® reagent is first dilutedin William's E medium (1:1 (v/v)) and then added to the wells of thespheroid plate. Therefore, ATP measurements in liver spheroids accountfor both intracellular and extracellular ATP content (i.e. total ATP).Luminescence is recorded using a FLUOstar Omega plate reader (BMGLabtech, Ortenberg, Germany) 30 minutes after addition of theCellTiterGlo® reagent.

Example 5

Determining ATP Secretion of Bronchial Organotypic Cultures and LiverSpheroids

ATP secretion into the airway surface liquid (ASL) of bronchialorganotypic cultures is measured following addition of hypotonic (5.2 mMKCl, 1.2 mM CaCl₂, 1.2 mM MgCl₂, 10 mM glucose, 10 mM TES, pH 7.4)saline solution. In brief, cultures are first washed with PBS and thentreated with isotonic saline for 5 minutes. The apical solution is thencarefully collected. 60 minutes later, cultures are treated apicallywith hypotonic solution for 5 minutes, after which the apical solutionis carefully collected. ATP content of the collected ASL samples ismeasured using the ENLITEN® ATP Assay System (Promega). Luminescence isrecorded using a FLUOstar Omega plate reader (BMG Labtech). The ATPconcentration is extrapolated from a standard curve.

Example 6

Gene Expression Analysis

RNA is prepared from lung and liver tissues using the miRNeasy Mini kit(QIAGEN, Hilden, Germany). cDNA is prepared using the RT2 First strandkit and mixed with RT² qPCR Mastermix prior to plating the mix on thePhase I Enzymes RT2 Profiler PCR Array (QIAGEN). qPCR is performed usingthe ViiA™ 7 Real-Time PCR System (Thermo Fisher), and data is analysedfollowing the instructions provided by QIAGEN. Fold changes with anunadjusted p-value <0.05 (t-test) are considered statisticallysignificant.

Example 7

Measuring Inducibility and Activity of CYP1A1/B1, CYP1A2, and CYP2B6Enzymes

Metabolic capability of both culture systems is further confirmed byexamining inducibility and activity of CYP1A1/B1, CYP1A2, and CYP2B6enzymes using P450-Glo Assays (Promega) according to the manufacturer'sinstruction. CYP activities are induced 48 hours prior measurement witha combination of 10 nM Tetrachlorodibenzodioxin (TCDD) and 25 μMrifampicin (Sigma-Aldrich, Buchs, Switzerland). 20 μM α-naphthoflavoneand 10 μM fluvoxamine maleate (Sigma) are used to inhibit CYP1A1/B1 andCYP2B6 activities, respectively. Once the measurements are completed,tissues are washed twice with PBS and returned to the incubator.

Example 8

Measuring Albumin Secretion

Albumin secretion by liver spheroids is quantified 48 hours after thelast medium change using the Human Albumin ELISA kit (Abcam). The samecell culture supernatant is analyzed for release of α-GST using theHuman α-GST ELISA kit (Wuhan EIAab, distributed by LuBioScience, Luzern,Switzerland).

Example 9

Measuring Cytotoxicity and Apoptosis

The ApoTox-Glo™ triplex assay (Promega, Dübendorf, Switzerland) is usedto determine the number of damaged/necrotic and apoptotic cells. Cellsare first incubated with bis-alanyl-alanyl-phenylalanyl-rhodamine 110(bis-AAF-R110) for 30 minutes to quantify the number of damaged cells.Then, the same spheroids were incubated with a specific caspase 3/7reagent to measure the number of apoptotic cells.

Example 10

Preparation of a Mixture of PneumaCult-ALI Medium and William's EMedium.

Complete PneumaCult-ALI medium is prepared by mixing PneumaCult-ALIBasal Medium (StemCell Technologies, ref. 05002) with PneumaCult-ALI 10×Supplement (StemCell Technologies, ref. 05003), PneumaCult-ALIMaintenance Supplement (StemCell Technologies, ref. 05006),Hydrocortisone Stock Solution (StemCell Technologies, ref. 07925) and0.2% Heparin Sodium Salt in PBS (StemCell Technologies, ref. 37250).

William's E medium (ThermoFisher Scientific, ref. 12551032) issupplemented with HepaRG Maintenance & Metabolism Supplement(ThermoFisher Scientific, ref. HPRG720) and GlutaMAX solution(ThermoFisher Scientific, ref. 35050061) to give Complete William's Emedium.

Complete PneumaCult-ALI medium is mixed with Complete William's E mediumat varying percentages, giving mixtures ranging from 70/30 to 100/0%(v/v) complete PneumaCult-ALI medium/Complete William's E medium.

Example 11

Mixture of Complete B-ALI Medium and William's E Medium.

Complete William's E medium is prepared as outlined in Example 1.

Complete B-ALI medium is prepared by combining the ingredients of theB-ALI BulletKit™ (Lonza, ref. 193514). Complete B-ALI medium is mixedwith Complete William's E medium in a percentage varying from 70 to 100%B-ALI medium. Complete B-ALI medium is mixed with Complete William's Emedium at varying percentages, giving mixtures ranging from 70/30 to100/0% (v/v) Complete PB-ALI medium/Complete William's E medium.

Example 12

Determining the Effects of Different Culture Media

The effects of the different media and their dilutions are assessed overa 9-day period by culturing the cells at 37° C. with 5% CO₂ and 90% ofrelative humidity.

The effects of the different media and their dilutions are assessed overa 9-day period. HepaRG cells are first seeded onto Corning® SpheroidMicroplates using the William's E medium complemented with Thaw, Plate,& General Purpose Supplement (Thermo Fisher Scientific, ref. HPRG770)and GlutaMAX solution. After 1 week of maturation, medium is exchangedfor a mixture of PneumaCult-ALI medium or B-ALI differentiation mediumwith William's E medium complemented with Maintenance & MetabolismSupplement. Percentage of Complete PneumaCult-ALI or B-ALI diluted inComplete William's E medium was 70%, 80%, 90% and 100%. 9 days later,spheroids are used for experiments. All the results obtained with themedium mixtures are compared to spheroids maintained with the CompleteWilliam's E medium only.

Example 13

Measuring Total Glutathione Levels

The GSH/GSSG-Glo assay (Promega, Dübendorf, Switzerland) is used todetermine total glutathione levels as a marker of antioxidant capacity.In this assay, spheroids are incubated for 30 minutes with either aTotal Glutathione Buffer (GSH+GSSG) or an Oxidized Glutathione Buffer(GSH). Following addition of a luciferin detection reagent, luminescenceis measured with a FLUOstar Omega plate reader. As the assay allows tomeasure the total GSH+GSSG and GSSG, it is possible to deduce the GSHamount in the samples.

Example 14

The results of some of the experiments carried out are summarised inTable 1.

Example 15

ATP Content of Liver Spheroids

A significant (P<0.05) ATP increase in all the conditions is found whenComplete Pneumacult-ALI medium or Complete B-ALI medium is used. Thehighest ATP content is seen when spheroids are maintained in 100%Complete Pneumacult-ALI medium with similar ATP content when using 70%,80% and 90% Complete Pneumacult-ALI medium. ATP content of spheroidsmaintained in Complete B-ALI medium is always lower compared to that ofspheroids cultured in Complete Pneumacult-ALI medium, and the lowestvalue is obtained for spheroids maintained in 100% of Complete B-ALImedium.

Example 16

Cytochrome P450 1A1 and Cytochrome P450 B1 Activity of Liver Spheroids

Activity of cytochrome P450 1A1 and cytochrome P450 B1 is significantly(P<0.05) increased in induced spheroids cultured in mixtures of CompleteWilliam's E medium and Complete B-ALI medium or in mixtures of CompleteWilliam's E medium and Complete Pneumacult medium. In induced spheroidsmaintained in 100% Complete B-ALI™ medium, cytochrome P450 1A1 andcytochrome P450 B1 activity is similar to that of spheroids cultured inComplete William's E medium. Basal cytochrome P450 1A1 and cytochromeP450 B1 activity is also significantly (P<0.05) higher in samplesmaintained with 70% & 80% of Complete Pneumacult-ALI or Complete B-ALI™medium.

Example 17

Assessing the Number of Damaged/Necrotic Liver Spheroids

Aside from the 70% Complete Pneumacult-ALI condition, the 9-dayincubation with the Complete William's E medium and CompletePneumacult-ALI medium/Complete B-ALI medium mixtures, significantly(P<0.005) increases the number of damaged/necrotic cells in allconditions. Moreover, an increasing amount of Complete Pneumacult-ALImedium/Complete B-ALI medium results in an increase in the number ofnecrotic cells. The number of damaged/necrotic cells is significantly(P<0.05) higher when using the Complete B-ALI mixtures compared with theComplete Pneumacult-ALI mixtures (when comparing similar % of mixtures).Apart from the standard condition, the lowest number of necrotic cellswas obtained with media mixtures containing 70% Complete Pneumacult-ALI.

All media mixtures significantly increase the number of apoptotic cells(P<0.05), with the highest numbers seen in spheroids cultured inComplete William's E-medium and Complete Pneumacult-ALI medium mixtures.The number of apoptotic cells in spheroids maintained in CompleteWilliam's E and Complete B-ALI medium mixtures is significantly (P<0.05)lower compared with the Complete William's medium and CompletePneumacult-ALI medium mixtures for the 70%, 80% and 100% mixtures (whencomparing similar % of mixtures). The condition allowing for the lowestnumber of apoptotic cells is obtained with 100% B-ALI medium.

Example 18

Glutathione (GSH) and Oxidised Glutathione (GSSG) Levels of LiverSpheroids

Culturing liver spheroids for 9 days in the various mixtures of CompleteWilliam's E medium and Complete Pneumacult-ALI medium/Complete B-ALImedium, the level of GSH is significantly (P<0.05) higher in cultureswith 70% and 80% Complete Pneumacult-ALI medium compared to the CompleteWilliam's E medium. Higher amounts of Complete Pneumacult-ALI medium donot further increase GSH content, but decrease them. Similarly, GSHlevels are significantly (P<0.05) higher in spheroids maintained inmixtures with 70% Complete B-ALI medium compared to Complete William's Emedium alone. As with Complete Pneumacult-ALI medium, GSH contentdecreases with increasing amounts of Complete B-ALI medium, eventually(at 100% Complete B-ALI medium) reaching a value below that seen inspheroids cultured in William's E medium.

With the same assay, the GSSG content is also measured. GSSG is alwayssignificantly higher in liver spheroids maintained in mixtures ofComplete William's E medium with Complete Pneumacult-ALI medium/CompleteB-ALI medium compared to the 100% Complete William's E medium,independent of the type of Complete Pneumacult-ALI medium/Complete B-ALImedium used or its concentration. While the GSSG content is onlyslightly elevated in spheroids cultured in Complete William's E mediumand Complete B-ALI medium mixtures above that of spheroids maintained inComplete William's E medium only, GSSG content is strongly increased inspheroids maintained with Complete William's E medium and CompletePneumacult-ALI medium mixtures.

Example 19

Albumin Secretion of Liver Spheroids

While albumin secretion of spheroids maintained with Complete William'sE medium is lower than the expected results (expected: 15-30pg/day/cell; obtained: 4 pg/day/cell (Gunness et al., 2013)), asignificant (P<0.05) increase in the release of albumin with all mediamixtures tested is measured. Secreted albumin of spheroids maintainedwith 70%, 80% and 90% Complete William's E and Complete Pneumacult-ALImedium/Complete B-ALI medium is significantly (P<0.05) higher forspheroids maintained with Complete Pneumacult-ALI than with CompleteB-ALI™ medium (when comparing same %).

Example 20

Gene Expression

Fold regulation of the expression of phase 1 drug metabolismenzyme-encoding genes in 3-dimensional organotypic lung cultures isassessed at 1, 2, 3, and 4 weeks. Gene expression is compared betweenlung cultures treated with TCDD and rifampicin for 48 hours (n=3) anduntreated cultures (n=3), and fold changes are calculated. All of thegenes shown in FIG. 7 are upregulated at week 3 in the presence of TCDDand rifampicin. All of the genes shown in FIG. 7 are downregulated atweek 4 in the presence of TCDD and rifampicin.

Example 21

Plates Used to Create Lung Spheroids

The plates used to form the spheroids are named Corning® spheroidsmicroplate (Corning®, ref. 4520). The cells used to prepare thespheroids (HepaRG) are thawed and immediately seeded into these plates.Since the wells are coated with an ultra-low adhesion surface, the cellsdo not attach and instead aggregate. After a week, the cells form aspheroid that can be further used for the experiments. CYP induction (ametabolic marker), albumin secretion (a metabolic and health marker) andATP content (a marker of health) are all increased meaning that thespheroids are healthier in these wells as compared to wells fromInSphero. Without being bound by any theory, this may be due to theincreased volume of culture medium that can be contained in the Corning®spheroids microplate. The secretion of alpha GST is strongly reducedusing the Corning® plates compared to InSphero.

CYP inducibility is maintained for two more weeks (with InSphero CYPinducibility is only maintained for 2 weeks while it is maintained for 4weeks with Corning®). The ATP content is found to be 30% higher duringthe first 3 weeks and 40% higher at week 4. Albumin secretion is alsohigher at week 2 (10% higher) and week 3 (20%) but it and then reachessimilar values to the InSphero plates. For the alpha GST release, alarge difference is seen at week 4 (50% decrease) and week 5 (63%decrease).

Example 22

Summary of Results

In this study, 3-dimensional organotypic cultures of the lung and liverwith respect to health, morphology and metabolic activity over a 4-weekperiod are studied. The results show that: 3-dimensional bronchialcultures maintained at the air-liquid interface have a stable ATPcontent up until week 3 and exhibit no morphological changes over thetest period. They retain the ability to produce ATP in response tostimulation during the 4-week period. In addition, 3-dimensionalbronchial cultures exhibit higher CYP1A1/B1 activity at weeks 2 and 3,while expression of several (but not all) metabolic enzyme-encodinggenes is elevated following induction throughout the test period (seeFIG. 7). HepaRG spheroids have a stable morphology, albeit with adecrease in ATP content and CYP1A1 and 1A2 inducibility and a minimalincrease in α-GST release over the test period. Unexpectedly, albuminsecretion decreases rapidly after the first week of culture.

Maintaining the spheroids for 9 days with Complete William's E mediumand Complete Pneumacult-ALI medium mixtures, ATP content, cytochromeP450 1A1 and cytochrome P450 B1 inducibility and secreted albumin areall improved compared to Complete William's E medium condition. At thesame time, the number of necrotic or apoptotic cells and the GSH/GSSGratio are negatively affected by the mixtures which may be a result ofoxidative stress. Tests performed with Complete William's E medium andComplete B-ALI medium mixtures also show an increase in ATP content,cytochrome P450 1A1 and cytochrome P450 B1 inducibility and secretedalbumin compared to Complete William's E medium. Using CompletePneumacult-ALI medium for co-cultures is suitable in certain embodimentsof the present disclosure. As one aspect of the disclosure relates to atwo organs on a chip system with interconnected lung and liver tissues,the use of 100% Complete Pneumacult-ALI medium allows the use of lungcultures without any further optimisation. As the liver spheroids appearto be maintainable with 100% Complete Pneumacult-ALI medium, it is asuitable condition for co-culture in the multi-organ-on-a-chip system.

Any publication cited or described herein provides relevant informationdisclosed prior to the filing date of the present application.Statements herein are not to be construed as an admission that theinventors are not entitled to antedate such disclosures. Allpublications mentioned in the above specification are hereinincorporated by reference. Various modifications and variations of theinvention will be apparent to those skilled in the art without departingfrom the scope and spirit of the invention. Although the invention hasbeen described in connection with specific preferred embodiments, itshould be understood that the invention as claimed should not be undulylimited to such specific embodiments. Indeed, various modifications ofthe described modes for carrying out the invention which are obvious tothose skilled in cellular and molecular biology or related fields areintended to be within the scope of the following claims.

TABLE 1 Comparison of the results obtained in each culture medium. Thefold change is expressed as compared to William's E medium alone. 70%80% 90% 100% 70% 80% 90% 100% P P P P B B B B CYP induction 2.9 2.5 2.32.1 2.1 2.4 1.9 1.0 ATP content 2.6 2.7 2.9 2.7 2.1 2.4 2.1 1.5 Albumin2.5 3.1 2.6 3.3 2.0 2.1 1.8 1.9 B = Complete B-ALI ™ medium at 70%, 80%,90% and 100% (v/v). At 70%, 80% and 90% (v/v) the remaining volume ismade up to 100% (v/v) with William's E medium. P = CompletePneumaCult-ALI medium at 70%, 80%, 90% and 100% (v/v). At 70%, 80% and90% (v/v) the remaining volume is made up to 100% (v/v) with William's Emedium.

TABLE 2 Composition of William's E medium Molecular ConcentrationComponents Weight (mg/L) mM Amino Acids Glycine  75.0  50.0  0.6666667L-Alanine  89.0  90.0  1.011236 L-Arginine  174.0  50.0  0.28735632L-Asparagine-H2O  150.0  20.0  0.13333334 L-Aspartic acid  133.0  30.0 0.22556391 L-Cysteine  121.0  40.0  0.3305785 L-Cysteine 2HCl  313.0 26.07  0.08329073 L-Glutamic Acid  147.0  50.0  0.34013605 L-Histidine 155.0  15.0  0.09677419 L-Isoleucine  131.0  50.0  0.3816794 L-Leucine 131.0  75.0  0.57251906 L-Lysine hydrochloride  183.0  87.46 0.47792348 L-Methionine  149.0  15.0  0.10067114 L-Phenylalanine  165.0 25.0  0.15151516 L-Proline  115.0  30.0  0.26086956 L-Serine  105.0 10.0  0.0952381 L-Threonine  119.0  40.0  0.33613446 L-Tryptophan 204.0  10.0  0.04901961 L-Tyrosine disodium  261.0  50.65  0.19406131salt dihydrate L-Valine  117.0  50.0  0.42735043 Vitamins Ascorbic Acid 176.0   2.0  0.011363637 Biolin  244.0   0.5  0.0020491802 Cholinechloride  140.0   1.5  0.010714286 D-Calcium pantothenate  477.0   1.0 0.002096436 Ergocalciferol  397.0   0.1  2.5188917E−4 Folic acid  441.0  1.0  0.0022675737 Menadione sodium  276.0   0.01  3.6231882E−5bisulfate Niacinamide  122.0   1.0  0.008196721 Pyridoxal hydrochloride 204.0   1.0  0.004901961 Riboflavin 376.0   0.1  2.6595744E−4 Thiaminehydrochloride  337.0   1.0  0.002967359 Vitamin A (acetate) 328.0   0.1 3.0487805E−4 Vitamin B12 1355.0   0.2  1.4760147E−4 alpha Tocopherolphos.  554.7   0.01  1.8027762E−5 Na salt i-Inositol  180.0   2.0 0.011111111 Inorganic Salts Calcium Chloride  111.0  200.0  1.8018018(CaCl2) (anhyd. ) Cupric sulfate  250.0 1.0E−4  3.9999998E−7(CuSO4-5H2O) Ferric nitrate  404.0 1.0E−4  2.4752475E−7 (Fe(NO3)-9H2O)Magnesium Sulfate  120.0  97.67  0.8139166 (MgSO4) (anhyd. ) Manganesechloride  198.0 1.0E−4  5.050505E−7 (MnCl2-4H2O) Potassium Chloride 75.0  400.0  5.3333335 (KCl) Sodium Bicarbonate  84.0 2200.0  26.190475(NaHCO3) Sodium Chloride  58.0 6800.0 117.24138 (NaCl) Sodium Phosphate 138.0  140.0  1.0144928 monobasic (NaH2PO4) anhydrous Zinc sulfate 288.0 2.0E−4  6.9444445E−7 (ZnSO4-7H2O) Other Components D-Glucose(Dextrose)  180.0 2000.0  11.111111 Glutathione (reduced)  307.0   0.05 1.6286645E−4 Methyl linoleate  295.0   0.03  1.0169491E−4 Phenol Red 376.4  10.0  0.026567481 Sodium Pyruvate  110.0  25.0  0.22727273

The invention claimed is:
 1. A cell culture comprising a 3-dimensionalliver spheroid and a medium comprising a mixture of Complete B-ALImedium and Complete William's E medium, the mixture comprising from 75%to 95% by volume Complete B-ALI Medium with the remaining volume beingmade up of Complete William's E medium.
 2. A 3-dimensional multi-organculture system comprising a 3-dimensional liver spheroid and a3-dimensional-lung epithelial spheroid in a culture medium, said culturemedium selected from the group consisting of a culture medium comprisingor consisting or consisting essentially of a mixture of Complete B-ALImedium and Complete William's E medium, the mixture comprising from 70%to 95% by volume Complete B-ALI Medium with the remaining volume beingmade up of Complete William's E medium.
 3. A method comprising culturinga 3-dimensional liver spheroid, or co-culturing a 3-dimensional liverspheroid and a 3-dimensional lung epithelial spheroid in a mediumcomprising a mixture of Complete B-ALI medium and Complete William's Emedium, the mixture comprising from 70% to 95% by volume Complete B-ALIMedium with the remaining volume being made up of Complete William's Emedium.